Who/What generates Bitcoin Hashes to be mined? Bitcoin miners decrypt hashes, but who or what encrypts them in the first place? After all, something must have encrypted it so that miners could find it.
"Decrypting hashes" is not really a correct way to describe the calculation, and nobody "encrypts" them, which is probably why you could find no information on this notion.

The hashes that miners calculate are based on all the transactions on the network, metadata and previous block hashes.