Wether it's wallstreet or some other party, the truth is that yes people do try to cause markets to crash in order to be able to buy cheaper.

I personally am not sure wall street is to be blamed for entirely. I also suspect there are some really big Bitcoin whales who have been in the game since the beginning, and who have likely been pumping and crashing the market since the start. After witnessing this type of behaviour first hand in much smaller markets, I have no doubt the exact same thing is done with Bitcoin on a larger scale.
The end result is that short term, weak believers are being shaken out, but long term the price will continue to rise as large whales accumulate more. They more they own, the smaller the supply, therefore a higher price. The way to win is to not sell, but instead hold and be patient and let them do their thing :)