Bitcoin has a market cap of 70 billion. This is very low when compared with the stock market or the gold market. There are many groups that can buy the total number of Bitcoin in circulation with a price of $4000. They can easily manipulate the market both sides up or down. Bitcoin 70% supply is stored in a very less number of wallets say 5%. Don't you think Bitcoin can easily manipulate and below $1000 is still possible?
70 Billion dollars still not small amount to manipulate and it was more than 10 times when we are at the end of last bull run so describing based on the current market prices is not good.The number of people involved on the crypto investments is very less when compared to traditional stock investments were most of the big company have their investments.
Bitcoin can be manipulated by the emotions of traders which can be done by lot of other external sources like news than investing and risking huge money.
In addition to the volume and marketcap. don't forget the size of the users, many people say that bitcoin users currently cover many countries and tens of millions of users. manipulation will not be that easy, not all user can be affected by certain ways to sell their coins so that manipulation occurs. manipulation is getting harder when the user gets bigger
Add in the the price of bitcoin . btc price is now expensive and the time will come that the price can grow more evenly due to the growing adoption . now if the price is already expensive i dont think that someone can easily bought it . thats only a reason that bitcoin is really hard to manipulate . speaking of manipulation , manipulation isnt a bad thing because it also helps investors to purchase more coins if ever manipulators dump the price of a certain coin .