It's not fully fleshed out in the novels, so you have to piece it out from various mentions and their implications. The two most informative descriptions, IMO, are from Dune:
"Then came the Butlerian Jihad — two generations of chaos. The god of machine-logic was overthrown among the masses and a new concept was raised: “Man may not be replaced.”"
and from God-Emperor:
"The target of the Jihad was a machine-attitude as much as the machines ... Humans had set those machines to usurp our sense of beauty, our necessary selfdom out of which we make living judgments. Naturally, the machines were destroyed."
OP's original claim was "enslaved by those who controlled the AI", which is rather different.
But, yes, I don't think that the books imply literal enslavement either way. It could be described as "enslavement of the mind" in a sense of humans themselves adopting the "machine-logic" and falling prey to it.
"Once men turned their thinking over to machines in the hope that this would set them free. But that only permitted other men with machines to enslave them."
"Then came the Butlerian Jihad — two generations of chaos. The god of machine-logic was overthrown among the masses and a new concept was raised: “Man may not be replaced.”"
and from God-Emperor:
"The target of the Jihad was a machine-attitude as much as the machines ... Humans had set those machines to usurp our sense of beauty, our necessary selfdom out of which we make living judgments. Naturally, the machines were destroyed."