To me it sounds like staking has a much more powerful snowball effect than mining and the gap between the wealthiest ETH participants and everyone else will increase faster under PoS.
Every holder who is staking is rewarded for staking, in proportion to their stake.
> To me it sounds like staking has a much more powerful snowball effect than mining
No, because issuance under proof of stake is much lower than that under proof of work.
The point of validating is to secure the chain, not to get rich. The more validators that are active, the lower the per-validator rewards, reducing compounding effects.
Also you lock-up capital which has an opportunity cost and must competes with every other investable asset. As the barriers to entry staking are negligible (just acquiring a liquid staking derivative like rETH, for example) it means that everyone willing to stake will likely do so which drops the returns lower, which may push some stakers out as they see better investing opportunities. So staking is likely going to have thin margins in the future and will give a rate of return that is fairly priced given its risk adjusted returns.
Last I saw, ETH mining was about 33% profitable. With mining rewards ten times higher than staking rewards, that means miners take home about three times more on their investment than stakers.