His feeling was that it was too saturated this time, that was the difference. Too many people got involved. There was too much institutional interest, unlike the 2014 crash where the pinnacle was really just chasing Dorian around by the media asking if he was Satoshi.
It sounds like your father is ignoring the properties of Bitcoin that make it valuable and instead think about it as some sort of fad like a beanie baby. Meanwhile Bitcoin keeps getting improved, last year we had SegWit, now Schnorr and LN are being worked on, in the future we'll probably have sidechains and smart contracts. Bitcoin's ecosystem is growing with more and more businesses adopting it, Lightning has potential to create new types of services. Bitcoin becomes more accepted as money as less and less people call it a useless bubble and ponzi. All these things can justify the price way above $20,000. You can't analyze Bitcoin as a stock, but you can and should analyze it as software.