I think he just approached Twitter like he approached building electric cars or rockets. The latter are both a series of (admittedly very hard) engineering and technical challenges to solve with few, if any, gnarly social or political issues to navigate other than those which inevitably arise in any growing or large company. The hard problems are all engineering and technical (probably regulatory too, in fairness). There will be a lot of failures along the way but, most of the time (barring things that are physically impossible, or orders of magnitude beyond current cutting edge manufacturing techniques), you can brute force your way through - or find an alternative approach - with enough R&D effort/money and enough smart people.
But Twitter is nothing like this: it's all about the people, the politics, the social aspects, and simply having an end goal in sight and pushing hard towards it isn't going to get you to where you want to go - in fact, where you want to go may not even be possible due to different cultural and legal constraints around the globe. No disrespect to any engineers at Twitter but the code and infrastructure aren't the hard parts of that business at all.
I don't know that I'd describe him as unprincipled, but he is perhaps quite naive along certain axes. I think this is actually relatively common amongst very successful people who haven't experienced that much in the way of substantial failure: they can be really bad at dealing with choppy waters when they arise (I've seen this from quite close quarters, as it happens) because it sort of deconstructs who they think they are. And you really only learn who you are when the going is tough.