I can imagine a realistic scenario when 95% of hash power disappears in a second.
A super massive solar coronal mass ejection could fry electronics on Earth and take out power in many areas for weeks. But if that happened Bitcoin's breakdown would be the least of our worries.
If btc has a 90% drop in a short period of time, a lot of miners would turn off their equipment
You meant the price of BTC? No, I don't think so. They will keep mining, they just won't sell, which will bring the price back up instantly.
If you think about it's a miracle the price is staying up as it is given that every single day 5,000 new coins are created and somebody has to put in $2M every day just to keep the rate up. Although nowadays it's not really staying up.