How can you be sure that cryptos are real and not just people

exchanges are essentially that. or at least they could be. that's why you take your gains off the exchange.

because i trust people to be assholes

I've thought about this too. Say I buy 2 bitcoins tomorrow. That's a lot of sats. Where did all of this come from? It's all pieced together. 10 million X 10 million X 16.5 million Xs how many it's been traded up until I buy.