It’s not about valuation, it’s about sentiment.
3 minute summary
http://3 minutes https://www.youtube.com/watch?v=-v6ZAY-8JzQ
an hour if you have it – David Hunter is very specific. 01/08/21
https://goldsilver.com/blog/a-stock-market-crash-of-65-80-this-year/
Jeremy Grantham’s article 01/05/21
https://www.gmo.com/americas/research-library/waiting-for-the-last-dance/
And finally a rebuttle.
https://theirrelevantinvestor.com/2021/01/05/one-of-the-great-bubbles-of-financial-history/