Syndicates take advantage of crypto for money laundering because it is easy to transfer funds across different countries without the hassle of funds being checked if it's legal or not. If you are transferring illegal funds crypto is the safest way because of the anonymity it offers and decentralization. That is why most people have a perception that crypto is illegal which is wrong.
This depends on the crypto currencies being used. There are a lot of crypto currencies that are not actually anonymous as you can still track where the funds go while fiat, you never know where it will go or where it went. People are taking advantage of the features of cryptos, I agree that most of the people are mistaking it as illegal but actually, they are taking advantage of it and it is not actually a scam or illegal.