Well, have a lot of people who manipulate bitcoin, but honestly, it provides many advantages in retaining bitcoin. Well, they can manipulate the bitcoin only those who have a lot of bitcoin, and most likely it can only be done by the exchanger.
It will be a lot wiser if the exchanger just stay away from price manipulation. After all, they are already earning more than enough money from all the transactions that's happening on their website. If they join the manipulation, they can just lose money. Why risk if you already have a goose hatching golden eggs, right?
If they lose money from doing a gamble in the manipulation (pump and dump), then it will require time for them to get back that amount of money from the exchanger site which is kind of a hassle imo because they could've earned much more instead
You seem to be confusing exchanges with exchangers
These are two different notions which refer to different services. In respect to exchanges as such and manipulation they can perform, if done right. it is 100% sure and easy money for them. They cannot possibly lose anything (unless they do something really stupid, of course) simply because they control both sides of the trade. Given that, they can easily earn money by front running the orders of their clients. For example, if they see two big orders (one Sell and one Buy order) coming in at more or less the same time which are basically offsetting each other, the possible negative spread between these orders will be the exchange's pure profit. Exchanges may not place orders immediately but allow some small and almost unnoticeable lapse while waiting in ambush for such orders. They will just place their own orders at a little below and a little above other traders' Sell and Buy orders, respectively. If they weren't front-running orders, they could only earn on the commissions, but with this technique in place they earn on both the commissions and the spread