Why would he not release Hillary’s emails before now, if he actually has them?
Insurance. If he released them, he has no leverage, and he is victim of a “robbery gone wrong” like ol’ Seth Rich. With them, he can put them in a vault with a dead man’s switch to keep her from whacking him, or offer them to her enemies in exchange for protection.
Why would he release the ‘best’ information he has. That’s his insurance policy.