Regarding reasons for decline there really seems to be an overindulgence in ignoring the effects of the ridiculously bad technical performance of Bitcoin. Consider this narrative:

1. I start hearing about the bitcoin bull rush in the news in December
2. I check it out on the internet, absorbing all kinds of prophecies of a new monetary system without banks. Most of the "blockchain" talk is greek to me but I do understand we're dealing with a technology enabling practically free transactions to anywhere in the world within 10 minutes
3. I want in! I get a wallet and buy some BTC. #feelsgoodman
4. Now for the reality check - my first transaction - either I'm sending to a friend / family member, an exchange or maybe even a hardware wallet someone convinced me I needed. Whichever the case I'm confronted with the choice of a 10+ USD transaction fee or the "for all we know your transaction may never be handled at all" option and all my personal faith in the technology is shattered in an instance. And even more so if I did pay the fee and happened to be sending to an exchange and still had to wait about an 1 hour while "waiting for confirmations" was going on (whatever the hell that means?).

So now my personal experience is that this bitcoin / blockchain stuff doesn't actually work as advertised and I can't make any use out of it. But... what about all these people on twitter and youtube who obviously know better than me who swear that it's the best invention since agriculture? And they're telling me that fixing scaling is trivial (which you'll believe unless you are an experienced programmer and you realize that Lightning Network is going to create more problems than it solves)? And the price is still rising so I'm still going to be rich?

Until the price wasn't ricing any more...

I really do believe this is fundamentally the biggest contribution to weak hands and fear in the market - that belief in crypto doesn't come from personal experience or working technology but rather through sect leader style influencers and FOMO.