Anyone smart would use a new wallet each time.

There was a time when this would work. But as we've seen with high profile taken downs, the folks like those at Chainalysis make it incredibly hard to obfuscate with any degree of certainty.

Withdrawals from Coinbase to would be indistinguishable from temporary insider trading accounts. And there are certainly a lot of withdrawals. And in many cases the trading happens off chain anyways

This isn’t true for Monero.

These are people who use coinbase (and I assume work for coinbase too) for sketchy crypto trading. Already not the smartest.

Why is this trading sketchy?

I mean to be truthful I don't find it that sketchy, but clearly somebody does

Not necessarily. If people buy after you trade then the value of your wallet goes up.

Could you explain further. I'm not sure I understand how this relates to the parent comment?

Imagine you you had a magic button that suddenly increased demand for a volatile security any time you pressed it. That would be a fairly valuable thing for some people.

If I have information that the price of x coin is going to go up and my friend knows I know, then they just need to follow my trades and they can make money too.

If enough people follow my trades then this can generate demand and actually affect the price.

It’s in their interest if other people copy their trades because the asset values will go up

Yeah. Bitcoin for example has rich lists: we know the addresses of whales and can track their movements via the blockchain. Some rich person suddenly moving hundreds of thousands in bitcoin to an exchange can be a potent sell signal.