People B did the initial legwork.
People C paid for the growth (which came from work they did elsewhere).
In the end, person A disproportionately benefited on the backs of persons B and C for the amount of work they did in the entirety of the outcome.
Yeah, person A is arguably merited a ROI, but the insane amount is what some people find is unmerited here.
That is the risk of losing the entire sum of what they put in.
Taking on that risk is where the disproportionate ROI comes from. Person C took way less risk.
In addition, I believe "Person A" in this case actually gave more help than just funds, ie legwork.
I believe there also lots of other versions of the same thing. For example if you bought lots of Bitcoin/Ethereum early on in its first year. It's just that its too risky for people to do that.
I also did mention that there was work put in in addition to the check as far as im aware.