What will happen if crypto vanishes overnight or due to some or the other reason if crypto becomes inaccessible to public? I know this does not make sense as crypto will not vanish but still what if it happens? What about those huge chunk of investments made by whales and other investors?
Those huge investments would become instantly worthless. But you said it yourself, this scenario makes no sense. Crypto could be banned or the internet could be cut off, or it could end up being a passing fad. At no point would it simply
vanish though.
Even if the internet went down worldwide, the blockchains would still exist, waiting to be mined once the network returns.