> But the central bank doesnt print money to throw it into a vault.
Correct, however US personal savings rates are at all-time highs. [1] So, you are correct, the banks aren't taking the money and locking it into vaults. However, people are taking their money and locking it up in savings accounts and investment accounts. This is reducing velocity. The "printing" was to offset this reduction in velocity and avoid a deflationary spiral. Through lending, so they can be used for productive things.
This also explains how asset prices spiked without actually causing inflation.
> Cryptocurrency gives them a way to protect their savings from that.
I don't want to get too far down this rabbit hole, but literally everything that isn't currency is inflation-proof. Inflation only affects currency. So, if you buy real estate, or stocks, or even un-productive assets like gold, silver or cryptocurrencies, you're equally protected from inflation. It may underperform, but now we're talking about rate of return in constant-dollar terms.
Cryptocurrencies do protect you from inflation, yes, but they have massive deficiencies that make them a poor choice relative to their peer investments, in my opinion. Such as the rampant fraud in the space. This hinders price discovery, and makes it impossible to determine a real value. It also causes massive swings of 27% week-to-date. That's an annualized inflation rate of 25,000,000% when measuring the value of a bitcoin against CPI.
[1] https://fred.stlouisfed.org/series/PSAVERT