Have you ever wondered why since it began in 2009 no one has ever been charged with running the bitcoin ponzi. Its because the missing link needed to prove a Ponzi is the explicit promise of a given return while relying on new money to fund the return. It may be true that some individuals have spun off into crypto and done this but thats not bitcoin it may be that some individuals may even start a fund promising that but thats not bitcoin its a fund using bitcoin. Bitcoin never promises anyone any return