It is a good question but here is my thoughts. The hedge funds / institutional investors aren't used to seeing anything that moves this fast as far as gains and drops. So in this ride to the moon they would likely feel that it is a bubble and if they are looking at the data from the previous crypto bubbles and other bubbles in other sectors it fits a lot of the criteria.
As far as weak holders being replaced...... possibly but what happens to people is that once it runs really fast they fill like they missed it.
It has even happened to me several times. But to reference 2013 I have a friend who knew about Bitcoin before me back in Indiana. Once the prices shot up insane and were at $800 + I asked him why he didn't get in and basically he said he felt like he missed it. In a lot of ways he was right. some of those people take positions later but a lot don't. So as the price gets higher then it messes with people's head especially if they can't buy an entire Bitcoin.
Same thing in the stock market. When the price of a stock get's high it messes with people minds feeling like they can't play on that level.