2. Other theoretical ways would be if a governing body for one of the other cryptocurrencies reversed a transaction, such as occurred during the earlier DAO hack. Another possibility is if some of the funds were left in an exchange’s custody - obviously a hacker would work to avoid that, but maybe they were rate limited or something before an exchange locked the funds.
The whole point of crypto, for me, was to be immune to central authorities who can reverse transactions.
That is an issue of inferior public and non-fungible crypto like BTC not crypto as whole. Monero XMR for example has none of these issues as one of the only actually useful crypto.
It’s probably those that have been seized, as the heist wasn’t entirely BTC.