I have a friend who does financial planning.
He is a lawyer, highly intelligent, and has been in the business for many years. For most clients, he puts them into high quality mutual funds handling only blue chip stocks. We were discussing the market, and how so many stocks, especially in the nasdaq were insanely over valued. He then asked me why I think investors would pile into so many stocks ie DOCU for so long, if they had and kept much higher than normal PEs going forward ie 100+, which could not be near justified by their earnings/revenue growth going forward. Here was my answer. I said, I have no idea, except that it's like if you present a lie as truth often enough, and are a good enough salesman, your lie becomes the truth, and if this truth is compelling enough, others will follow.