If anyone create a altcoin with very low supply like only 3k which is 10x smaller than YFI, then that could surpass yearn finance maybe with 10x more value which Won't be wondering but yeah, as far i know, only YFI surpassed btc value for first time. Well i don't Have much to say about YFI. I doubt about its existance cause similar project like YFI come in market as well as performing better than it
not sure all low supply coins can be like YFI. I think the determining factor for YFI to reach the current price is that the YFI concept is in line with the roadmap and that could be one of the things that makes the public market respond well to YFI. I think that is the real factor