About the decorrelation, check website out: https://www.sifrdata.com/cryptocurrency-correlation-matrix/ and check the 365-day correlation between BTC and SPX (S&P 500 index). It is pretty much 0 and in the last 9 days it was even quite negative :-)

And I agree there were talks already on 2014 about Bitcoin and crypto, but those were mostly that, talks. Nowadays countries like Canada, Singapore, Switzerland, Japan and China have quite some clear regulation (even though a lot more has to come). Also Bitcoin Futures are actually there and legal on the CBOE and CME. Next to that, I feel there is a lot more pressure from the financial status quo + entrepreneurs for clarity on regulation than in 2014.

Interesting thoughts about the decoupling of altcoins from Bitcoin. I havent's put in much thought on that one. As long as there are no mainstream use cases in which altcoins are used on a daily basis (and with and actual business model), I don't see any reason for decoupling though. Everything is just speculation until then. But as I said, I haven't looked into it that much yet. I generally look at things from a macro-economical perspective :-)