This happened in the early days of Bitcoin. There were times when one miner mined several blocks and one device did the mining. If this happened, the difficulty would decrease greatly and the network would stop until someone mined Bitcoin and the blocks continued to work.
Except it there is bomb to stop all Bitcoin miners at one day, Bitcoin network hashrate will drop gradually and network difficulty will retarget gradually each 14 days roughly and with lower hash rate, difficulty will become lower too, new blocks will still be found be smaller miner community.
However, if there is a bomb, the network will become a dead one and it will need a new recovery, reinstallation of miners massively to revive the network and find new blocks.
The price of Bitcoin will fall sharply, and it will be more vulnerable to centralization or successful 51% attacks, but the value of Bitcoin will definitely not be so low that it reaches zero dollars.
When price was too low, nobody minded to attack Bitcoin network because they possibly thought it is a joke, does not worth to attack and Bitcoin is useless, valueless or will die soon.