Ah, I see. Your problem is a fundamental lack of understanding of financial markets. I'd recommend Investopedia as an easy way to get into understanding things.
First of all, in financial markets there is almost never a "fixed number" of buyers for anything, and especially not for something like Bitcoin. If you want to see something with (as good as you can get) to a fixed number of buyers, look at uranium. It's almost entirely used as fuel for nuclear reactors, which take years to build and to be shut down, so not only is the demand very stable, the future demand (for the next few years) can be pretty easily predicted. You'll be surprised to see that yes, sharp price drops can occur, even in such conditions.
Next, of course, the market of sellers for Bitcoin, "HODLR" or not, certainly does not behave how you imagine. Some sellers are forced to exit large Bitcoin positions every day, with reasons ranging from tax liabilities not payable in Bitcoin, businesses that accept Bitcoin that do not wish to maintain a Bitcoin position, divorces, governments that seize Bitcoin, etc etc. Then of course you have people exiting Bitcoin because they're people and life happens: their partner told them Bitcoin was stupid, or their government added rules to holding Bitcoin that scare them, or they read that a shady entity was printing billions of fake dollars to buy Bitcoin, or they bought in years ago and wow, they can buy a car with the profit! or they bought in yesterday and the drop in price spooked them.
None of this is to say anything about the price of Bitcoin or if you should buy Bitcoin - I'm just saying that your _reasons_ are deeply flawed.