From what I've seen, Linus has always been mostly quite reasonable and constrictive, even before his 2018 "refection" that some others mentioned. Most of the time it was direct, but helpful, polite, and constructive. This is probably a big contributor to Linux's success.

It's just that on occasion he would rant and rave to people and call them retards or whatnot. People get a bit of a skewed perception because only those messages make the news and are famous, but that's not really representative of all the messages.

And when he did rant and rave, it was pretty much always towards established contributors who had screwed up somehow; people who in his opinion ought to know better, and most of the time he did have a good point. I don't approve of his style, but it's not like he would randomly call people idiots. It's not as if you ever ran the risk of being scolded by Linus if you were a new contributor sending a patch or anything.

tl;dr: Linus has always been like this, and was just occasionally an asshole.