One more thing, ppl should really not forget are the
BTCUSD Futures. Banks are interested, in pushing BTC price down, as they are the ones with the biggest harm if a decentralized money system would take over the world, right? So in Dec 2017 the banks came up with BTC Futures and shorted them like hell... what happened? right, 2018 happened
over time, the banks closed their shorts, which equals in "buying" the futures contract. So I would be careful with buys right now, and wait if the banks who have nearly infinitive money at hand, are trying to short BTC futures again, and this way makes many ppl. sell their BTC as well, what would only accelerate a possible BTC drop. I am not saying this is what is going to happen, but it certainly is a possibility.
So Banks and their Future Contracts have a big interest in moving BTC as well.
I wouldn't really say that banks would want bitcoin to fail, mainly because banks are getting involved as well. Think of it this way, if they try to make it go down, they will have to work hard on it, and since governments are already taxing and allowing bitcoin, that kind of means we are not really in a bad situation neither in public usage, so it would be a very big task for banks to stop it.
However if banks decide that instead of fighting it, if they decide to use it and make more money with it, they could use it in a bad sense. Obviously banks main purpose is to make money, and how can they make money? They could simply just buy bitcoin and wait? They will not do that, they will definitely do a whole "buy bitcoin" thing and you buy bitcoin from them, but then they will package a 1000 bitcoin deal together and sell that too, and then have 100 packages of the 1000 packages and sell that too, basically they will make money from bitcoin going up or down, doesn't matter.