It comes from Twitch [1]. While it often refers to streamers, it has transcended that. An andy is someone who is identified by whatever adjective is applied. So a Crypto Andy is someone who is all and only about crypto, basically.

Put another way: Andys are indistinguishable from each other apart from one defining characteristic. And those Andys with that characteristic are likewise indistinguishable and interchangeable.

[1]: https://knowyourmeme.com/memes/andy-slang