imagine all those people who sold Apple, Microsoft, Amazon in the 1999 bubble. I bet they own those stocks again, probably cashed out and bought a lambo, only to buy back the shares at double to even 10x the price. will the same happen to bitcoin?
If you sell an appreciation asset and purchase a depreciation asset like Lambo or anything of that sort people do not usually sell a depreciating asset to enter the market again but they will enter the market because they had the opportunity to make big profit in the past and if they find a suitable market situation to enter again they will do that but that does not mean they need to sell their assets to enter again.
If you purchase a costly item with all of your profits then i would say they are crazy.