They didn't buy all the bitcoin. They dictated the price that they would reimburse the unfortunate victims of that Executive Order (6502).

It would be like me walking into 7-11, grabbing a 2L bottle of Coke, tossing $1 on the counter and walking out -- because I deemed that a 2L of Coke is worth $1.

Theft, it would be, in that case.

Just as it was theft in 1933.

And in 1933, it wasn't "all the gold", it was gold held for speculation, in the U.S..

Most of that gold held for speculation was held where it could be kept secure -- in bank vaults, or with custodians.

The holders of gold back then (as is the case today as well) could not easily and securely store the gold by themselves. For if they had, that executive order would have been little more than a good laugh. Just as would a similar Executive Order today where the commodity being confiscated is bitcoin. (Well, those who have their coins on exchanges would lose access to them, but those who hodl their key would not be affected much.)