Bitcoin will become mainstream when people get pissed at their governments for rugpulling them with fiat. Until then, it will mainly be a store of value and I'm sorry to say, most people will prefer a custodial service protected by insurance and the justice system.

When I say "most people" I mean anyone born before y2k. Bitcoin is a generational solution, it makes central governments obsolete, and there is no such thing as bitcoin failing.