You seem to be assuming the platform is a random, representative sample of the general population, which I don't think holds up. I think it's much more likely that there's a reason the platform skews left, and my guess is that it's a mix of:

• the devs are pretty hardcore socialists, so the people who could put up with that in the early days were left-leaning - this is backed up by lemmy.ml generally being more leftist than most other instances
• people too far right for other platforms probably already left for places like Truth Social, Voat (is that still a thing?), and similar platforms
• people too far left for other platforms didn't have a clear place to go AFAICT
• people annoyed by Reddit's corporatism probably lean more left on average; Reddit already leans left, so this would attract the more extreme of that population

That's my take. I honestly don't read too much into it, so I generally don't bother with the political posts because the discussion seems a bit too group think-y to really be constructive.

If you have statistics from a broad, random sample that demonstrate that lemmy opinions are well distributed, I'm happy to change my mind. But "eat the rich" as a meme here really isn't a thing I've experienced in real life, so I really don't think lemmy is all that politically diverse.