I am not sure that is a bubble for bitcoin knowing the fact halving happened this year. Most probably to see an altseason would be in the spring of 2021 if we are looking back at 2017 chart
Halving could not be a strong reason to prove why this is not a bubble but the strong proof could be there were so many billionaires started to take some portions from their portfolios to be used by bitcoin. This brings massive adoption to the bitcoin. Various funds management platforms were also starting to buy bitcoin or at least suggested its clients put some percent of their portfolios to the bitcoin.
Paypal's effect was also playing a lot in this case.