All bear markets started after something collapsed or was proven to be a hyped up bubble (ICOs). With the increasing institutional involvement in crypto, it's very likely something they control will cause the next bear market. Maybe ETFs, maybe something else. But investors in ETFs will at some point start selling hard to take profits. At which point, Microstrategy won't be able to buy everything they sell. Sure, they may start selling more after an event that starts a massive FUD. But there's still time until then...