Don't you think this is rather the rule rather than the exception?

I don't. For someone holding a large number of tokens, it wouldn't make much sense to force the price down. If anything, they would push it up so they can dump, then quickly re-buy for another pump-and-dump later.

A slow, gradual price decline doesn't tell me that there are a few people colluding to decrease their net worth. It just tells me that there isn't much interest in buying the token at the moment at the market prices, for various reasons. There was a rather quick spike in prices. A slower correction is expected until a new floor is found. It could be at current prices or it could go lower. This isn't really anything outside the realm of asset/currency markets.

And I don't think it's meaningless to analyze patterns for pretty much anything. But recognizing patterns is what trading is all about, whether those patterns are a result of collusion or not.