I think it's wrong to compare the old bear market history with the future bear market, things could play out differently, I was into crypto in 2019 and I am very sure that there was a bear market years back before 2017, in 2020 there was pandemic, no one saw that coming.
Apart from bitcoin other markets like forex traders, etc they all partly fix their mind in past occurrence in the market at a certain period as a guide in addition to their present analysis of the market to be able to know or have and make a good/successful trade's decisions.
How do you get a hint sight about possibility of outcome of future trade without past historical experience of how such market has been playing out in times past. The future outcome may not be exactly as the past occurrences but some nuances could be perceived and that's why people take a major concern in market history.