The ultraconservatives already left for gab and truth social. There are some conservative instances and a few nazi ones as well, but the aforementioned two scooped up most of right wingers willing to jump ship.

Lemmy is more centrist than Reddit

(other than the usual issues) Reddit was hated by the general populace because it was too right wing and it was hated by right-wingers for not being right wing enough

Lemmy is still new and hasn’t gained a large population as of yet, but it’s already still far more representative than Reddit ever was

Just speculating here. And building off some half-remembered On The Media pieces. But as (for any number of reasons) the faith in a social platform collapses (and often the safeguards against toxic stuff go down too, a la Twitter), people with a low tolerance for that shit are likeliest to bail and the 'call people the N word on Xbox' folks are likeliest to stay behind. People who could watch what Reddit did and stay behind aren't bad, I'm not saying that, but their tolerance for unethical stuff is way higher than the tolerance of those who decided to find a new home. Self-selection, ya know.

Fortunately, this happened mostly on political-related topics

It is driven entirely by the moderators. r/Canada got taken over by alt-right moderators which attracted alt-right redditors.