> I wonder what it is about Crypto that causes large players to cover user loses.

The answer is in the comment you replied to:

> there are a lot of awfully rich people who are scared of the bubble popping.

The value or cryptocurrencies depends on hype and on convincing the next chump that they should buy in. The large players have a lot of money invested which they will lose if the cryptocurrency value tanks because people lost trust. Covering user loses is itself an investment; it contains the damage by making the issue die down.