The Bitcoin dominance, until then close to 100%, took off the road in 2017 with real Tulipomania, sorry, I meant: Altcoinomania.
I don't invent this burlesque qualifier of Alcoinomania by chance!
It was indeed a very intense and short-lived speculative bubble ...
... like Tulipomania, the first crash in history (1636-1637).
From the ATH of altcoins dominance in late January / early February 2018, the bubble burst.
2018 ... 2019 ... 2020 ... this gradual bursting, punctuated by "dead cat bounces" on the altcoins market share, has thus gradually made Bitcoin take the ascendancy back, by true safe haven.