ELI5: Decentralized exchanges and "presales"

I've recently started using Uniswap. It's great, apart from all the scams. Short of just rugging, there seem to be a lot of new projects that have their liquidity provided through a "presale", which seems to be just the developing allocating tokens to his own wallets to later dump. Aside from from that, the majority of these projects offer fake promises (Coingecko listing soon! etc), and encourage other people to shill for them. What I'm wondering is how is this so commonplace? Is crypto really that much of a greyzone where creating your own project and then dumping on the people who buy isn't actually illegal? Is this just the same group of people making new projects over and over again? Both? I'm just having a hard time wrapping my head around this.

If anyone more educated on this topic could perhaps explain this to me that would be much appreciated. Google seems to bring up ambiguous results.

My apologies if this question does not belong here. I figured since Uniswap is an exchange for ERC20 tokens this might be an ok place to ask.

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Thank you.