There's no need to believe, it's all public data and many thousands traders/bots are using those to trade every day... if the orders were fake it would be known and arbitraged very quickly.
Talking here about all the major exchanges with actual volume (Coinbase, FTX, Binance, etc) of course might not apply to some scammy third-tier exchanges with no volume.
> There's no need to believe, it's all public data
Well I don't think you quite imagine the sheer amount of requirements a regulated exchange has to through.
Though I don't think major crypto exchanges (Binance, Coinbase,...) are blatantly cheating per se, they are still light years away from having the same level of compliance as traditional SEC regulated exchanges.
> if the orders were fake it would be known
Also, you seem to only consider obvious fraudulent behaviors, but there are literally millions of ways to exploit order flow when you're an exchange or broker, that are completely impossible to see from the outside.
Talking here about all the major exchanges with actual volume (Coinbase, FTX, Binance, etc) of course might not apply to some scammy third-tier exchanges with no volume.