Don't necessarily mean technical work, anything that would cause you to think of them.
2 - Casualness in the face of problems. If a junior came and told him that production was down, he would just laugh and say something like "ok man that's gonna be a fun story next Friday, let's take a look". That mentality of "everything is solvable, nothing is worth being angry at" was really contagious.
3 - If he didn't believe something was good, he wouldn't do it just to do what's expected. That includes canceling meetings we were invited to with a "nah this can be an email", making technical choices that were against common knowledge at the time if he felt it made sense, or being fully honest during daily meetings, sometimes saying things like "yesterday I didn't do anything productive whatsoever. I was not focused, but I expect to perform better today". Again very powerful as a formative experience for junior devs, as the honesty was a total antidote to impostor syndrome.
He was a great dev in technical terms as well, but I don't think his technical choices mattered even a fraction of the leadership aspect.
#2 is a big one, personally.
When I started, and was on call, every page was an 'omg omg' moment, and your brain rattles as you stare blankly at the screen. And I noticed nearly everyone is the same way, at some point at least.
But when I wasn't on call, and people called me to help anyways, it was much more relaxed(hey, not my butt this time) and it was a very level-headed approach.
Eventually I learned to just internalize 'be calm, we got this' even when flying solo, and it helped tremendously. Unfortunately, I have no advice as to how I actually achieved that over time.
But you need to have those memories in the first place, so the first mistakes are going to be tough. I now try to be that casual person for newcomers, because I know the reaction of those around you causes a big difference in your stress levels.
I've done this, and it went down really well. Even if you can't cancel the meeting, you can send a single person instead of the whole team. You can also send people back to their desks if their part in the meeting is over. I was also adamant on all meetings having some sort of description and agenda, so that people can tell if it's worth attending or not. That was more difficult.
At the beginning I thought, "fuck me, recruitment failed miserably on this one...". I just couldn't see how he was going to be a good fit for a company that mainly worked in the Microsoft ecosystem, of course, his project was a separate thing, or so they told us.
This guy was able to literally just sit there and code on HIS OWN laptop, some banged-up dell latitude, for 7.5 hours non stop... His OS of choice was Slackware and believe me or not, he carried a Slackware live cd at ALL TIMES!
After work we used to go for pints to a pub and he used to piss all over Microsoft and the company and myself and in general was very funny.
He shared some of his projects and among other things he had an incredibly 'tricked' tetris implementation in D, I always thought it was poetry made code... Other that that, the product was absolutely commercial...
At the same time, he had an incredible set of... oddities... He was always late! always. Used to leave tea bags sitting on a napkin next to his desktop for hours. Half eaten sandwiches on top of his laptop. Never flush the toilet (NEVER), and a collection of other incredibly inconsiderate behaviors...
In the end he clashed with a product manager and was sacked on the spot. Not for lack of technical knowledge. This guy was a mastermind...
"J. E." was named "James," but by the time I met him he'd given that name to his son and insisted on being JE only. He was "a mule following farmboy too unschooled to serve in the infantry" in WW2, so they had him make runways on various Pacific Islands with a bulldozer. He got really good at it, and bought himself one as soon as he got home.
When I knew him in the 80s he was the proprietor of a successful farming business, as well as a fairly large construction company focusing on earthwork. 50 employees and who knows what revenue; they didn't pinch pennies. He "ran" the company by choosing good managers, and spent his actual time working with whichever crew he felt like that day. He was often to be found in the shop with the mechanics, fixing the equipment, creating new hydraulic valves on the lathe for fun / to save buying a rare part for a 30 year old machine, etc.
He was truly unschooled, any math more complicated than money confused him and I think he had trouble reading. He was fiercely smart, and just believed "book learning" wasn't for him. But he was always eager to help teach the things he knew to his crews, and even more eager to learn new things, as well as eager to help others learn. He taught me more about road building, dam and waterway engineering, and the surface geology of our area than I can describe. Having him explain (a) what this chunk of metal was going to become (b) why it needed to be that shape to fit into an engine, and (c) watching him make it ... was true magic.
When we got the Italian "Maxi-Cultivator" machine that was so complicated only 3 people on the planet could keep one running, it was another entire education to watch this Tennessee Good Ole Boy dive into the machine with the Italian mechanic (and hapless translator who was having severe "Deliverance" phobias) and critique the design choices and implications of differing terrain. There was surprisingly little discussion of the parentage and morals of various parties, considering the issue at hand was a half million dollar planting machine that couldn't penetrate clay.
He truly was an artist will a bulldozer. He could use that tool to shape gravel on a hill the way a child smooth sand with a hand. "Feel everything the machine has to say to you" and "take care of your tools and they will take care of you".
They ran old equipment and were constantly rebuilding it; the intimate knowledge of the machinery was worth more than the money saved from economizing on capital. He really just liked having a huge junkyard of old, big scrap iron around. When he got to use some of it he was delighted.
He would sit and listen up to an hour or more just hearing about your life, with maybe only 5 minutes dedicated towards crisp work stuff. Just happy to just listen.
He left before 6 everyday, no matter what, always working 40 hrs a week.
He had a lot of tragedy is his life, and emphasized how work was a secondary concern to family and other kinds of fulfillment.
He never had big ambitions to make a splash. He taught me to be content with the craft, even our decades old code base had its own challenge and fun.
I didn’t care that I worked on not-cutting-edge work. Working in that group was some of the most fun I’d had my whole career.
He taught me that it’s often best to let go, be selfless, and don’t let the larger machinations of power brokers get to you. Really care for the people and relationships around you, and you’ll be rewarded in riches more valuable than money or professional prestige.
To this day he does everything in PMATE macros, and is always, always hacking the world. He once entered a shortest program contest, his entry was 2 bytes long, and did two things, test and count the amount of RAM in a system.