I dont think that is the case.
Left leaning people are just much less accepting of authority, so there are more likely to move of of reddit. right leaning people also tend to be more conservative, so they are more likely to stay on there old platforms.
There have been many right-wing exodus from reddit over the years. All of them have centered around a perceived "free speech" issue, and they have always flocked to the most promising alternatives (e.g. Voat). Obviously Lemmy with its origins was never seen as particularly appealing for that crowd. This time the issue just happened to touch the left-leaning part more.
Knock on wood, but Lemmy's grown to the point now that it almost completely replaces Reddit for me. The only reason I still stop by Reddit is for more niche fandoms that haven't taken off here quite yet.
Yeah, there's that one shitty instance pretty much everyone defederated from a week or two ago.
It's actually one of the oldest instances, over a year old. Because the worst far right trolls that got ip banned from reddit came here when they couldn't make a new account on reddit.
I think it's a different political dimension entirely isn't it? You have left vs right economics, and then authoritarian vs libertarian governance. I don't buy into that stupid political compass, but the axes do seem accurate.