VC companies do not dig into the numbers as you suggest. FTX was able to get away with their fraud for a long time for that very reason. VC companies don’t care if some of their investments are fraudulent as they spread their eggs so thin that it doesn’t matter if any given basket blows up. VC firms stated this to the press outright when FTX blew up.

Also most crypto companies are not good for laundering since the blockchains record that fraud forever and publicly. I could see some specific protocols where that may not be true — like monero or tornado cash — but these projects are not really startups. Most crypto startups pitch their products for enterprise customers and thus would be horrible for laundering money.