The reason why these manipulations are possible with other assets is that other assets don't actually gain much (if any value) over the years. Bitcoin is doubling in value every year, so shorting it long-term is out of the question.

Maybe, or maybe not. Many would posit that gold and silver would be going up significantly in value were it not for significant price suppression by the financial institutions and possibly governments. Maybe bitcoin is doubling every year because "they" aren't trying to suppress the price - yet. I don't really know either way, but I think it's dangerous to assume that it can't happen with bitcoin.

In any case, the point is just that if everyone holds their crypto on centralized exchanges, then they have all of the power just like with other assets. If it's not shorting then it will be something else. Crypto allows us to not require centralized financial institutions and I really hope all this $GME nonsense opens people's eyes to the need to take advantage of that.