> They can use their bank account to buy crypto and then pay the ransom.

This is actually more difficult than it sounds. Most banks and crypto exchanges won't allow a person to make meaningfully large crypto transactions without some account history.

Companies do exactly this frequently to get their hacked servers and data decrypted.

“Hey, cryptocurrency exchange, I, a random rich person, would like to, having never interacted with you before, buy a million dollars of bitcoin and transfer it out. Today, please.”

That is simply not going to happen.

Eh, million dollars would not raise a single eyebrow from an exchange side. Your bank, maybe, will have some questions about the transaction, but the things they can do to prevent you spending your money are thankfully fairly limited.

How long do you think it takes to create an account, get your KYC documents verified, get your trading and withdrawal limits raised to a million or more, transfer funds from your brokerage account, buy tokens and then re-verify when you try to transfer the tokens out of the exchange?

You'd be lucky to complete this in less than a week.

It takes about 3 days on kraken. Much less than a week.

Kraken is literally warning about delays in opening new accounts and getting verified right now.

https://imgur.com/a/k8zuSH1

My experience with banks in UK / EU is that they will bother you for much smaller amounts than 1M. I had banks bother me for 10k transfers and other banks completely ignore me for 100k transfers.