Bitcoin can not drop to zero, it is not like other altcoins that does not have value in the market. If Bitcoin is experiencing the bear market that doesn't mean the price of bitcoin will drop to zero. It is only shit coins that have the tendency to drop to zero.
what you say is true, because bitcoin is different from altcoins, and if for example the price of bitcoin goes down very deep I think people will definitely sell altcoins and will switch, that is, they will definitely buy bitcoin. so my view is also bitcoin will not touch zero price.