Bitcoin legal tender boosted Bitcoin market in El Salvador in 2021 but I don't think it will be a main contributor for Bitcoin adoption in future. Considering that in the USA, people can use bitcoins for many things even it has yet been legal tender there. The same with Bitcoin adoption and usage in other countries globally, I see Legal Tender is not mandatory for Bitcoin adoption growth in the future.
Bitcoin does not need to be a legal tender to be accepted in businesses; it only needs to be recognized as a mode of payment, not making it mandatory for businesses to accept it as payment for debts or obligations. Although being a legal tender boosts the confidence of merchants in Bitcoin, it is not necessarily needed to be a legal tender for merchants to accept Bitcoin as payments.
This page should be updated for Bitcoin is not a legal tender in El Salvador anymore. Due to the pressure from IMF, El Salvador removed Bitcoin being a legal tender early this year.
[1]