Couple of answers:
1/ you are smart enough to foresee the end of the bubble and you withdraw before
2/ you short the BTC in order to cover your portfolio
3/ you sell your portfolio and buy ripple. Ripple is disconnected from the Bitcoin and Ripple blockchain. So, if there's a crash, Ripple shouldn't be too much impacted. By construction, Ripple should be a stable coin in order to make transfers between banks stable and fast.
4/ you use tether. This coin has a bad reputation but it's a solution.