According to Gemini, index funds in total own about 20% of the value on the Nasdaq 100 index. So if you list a new company in Nasdaq, typically they have to buy 20% of it. But only about 5% of SpaceX will floated, which means there won't be enough shares to go round.

They are doing a bunch of changes to rules to try and make this not completely break, but even if it doesn't, it feels like index funds are going to have to buy a lot of the SpaceX float, which is going to make it look like a successful IPO even if hardly any real investors buy it.