However, I don't know why big guys like Saylor and Microstrategy chose to buy Bitcoin at peaks like newbies. If they want to accumulate Bitcoin, they can do it more aggressively when it was about $16,000 few months ago.
They bought their latest coins at 28,000 usd per BTC, that is not at the peak, and it is far away from it. If they had bought at 16k usd per BTC, people would still ask why they didn't wait to buy when it was cheaper. I think MicroStrategy are timing their BTC purchases very well, they are holding a total of 140,000 BTC's, bought at an average prive of 29,803 usd per coin, that is a very good business for them, their buying intervals make it easy for them to make a lot of profit in a bull run or even in a short pump.
I also do not think they can just buy anytime when they see the price is low, like how individual investors do when they have the money, MicroStrategy is a company, so there has to be a process to release funds for BTC's purchase, they cannot make sudden purchases.