Its kinda hard to do, blockchain needs a connection to verify any transaction over the network. If no connection, then no one can verify it, means its cannot be processed.
Yes, and in the end cryptoqurrency holders, stock companies and some businesses in the digital world will stop instantly, of course it can be fatal, especially not being able to cash out your investment. sometimes I also think about this if in the future the internet dies then there is no hope anymore.