You know that old scammer trick? Pick 512 wealthy people, pick a stock, write half of the the people the stock will rise, the other half the stock will fall. Wait for the real development, dump the addresses of the losers, pick a new stock and start again. Write one half stock will rise, other half, stock will fall. Repeat until only one address is left. Now give him the opportunity of an large investment. You have shown your skills because you were right 10 times in a row.

Mostly it’s random chance. The reality of investing is that it’s mostly down to chance. Take an equally skilled set of investors and give them the same market access and some will do exceptionally well.

Simple answer, it's impossible that all people choose the wrong investment even if you just choose by chance. It like playing the lottery, why do some people win? Because not all can lose all the time. And as soon you reach a certain wealth level it's easier to keep that level than to reach it in the first place, unless you are in idiot.

Luck, usually.

Mostly luck.

I read this more as “make sure to account for survivor bias and don’t say stupid stuff.”

Survivor bias doesn’t mean that everything is a fluke. It just means that some things are flukes and it’s important to include that in our models so we don’t think something random is non-random.

This is very different than everything being 100% random.