They don't need crypto to push out cash. They can already do that with debit cards. What does crypto have to do with it?

Crypto is decentralized. All government can do is establish their own crypto currency and try to outlaw the others. Even there, at most they can ensure that crypto exchanges don't exist, but they cannot prevent actual crypto transactions without shutting down the internet (which would bankrupt Big Tech). If you doubt the ability of crypto to circumvent the government, just look at the dark net which runs on crypto. Try running a dark net operation with gold or silver.

If you put all your eggs in cash, you've put all your eggs in the hands of government controlled, centralized currency. If the government demonetizes cash in exchange for a bank transfer of the same amount (was done in India a few years ago, but instead of bank transfers they issued new notes), what are you going to do?

Take some time to understand how crypto works. It's no different from gold, with the benefit of no counterfeits and long distance transfer and the drawback of relying on the internet and electricity. Also crypto exchanges may be outlawed suddenly (the same could be done for gold too).