"A bubble is an economic cycle characterized by rapid escalation of asset prices followed by a contraction" (Invesopedia). So, we have not seen a (large) contraction, thus is not not a bubble (yet). We would not know if we are in a bubble or in the initial growth of the asset. The same applied to Tesla.

https://www.investopedia.com/terms/b/bubble.asp#ixzz52UmAbHG4