Yeah before you needed soldiers and many of them so you couldn't add all of them to the 1% of elites. Those people were obviously sympathetic with people not from the 1%, so you could only go so far until the soldiers mutinied or just... didn't fight the revolutionaries with the zeal needed to be successful. With AI you'll have way better tools at your disposal. You can man a 24/7 control room of 10 people hating the poors, all made up of 1%ers, controlling an army of 10 million robots.
But on the other hand, elites themselves also have hierarchies. There used to be kings, lower nobility, higher nobility, etc. Those would fight all the time about how much power each of them had. If the top 10% of the human population had a secret meeting to kill the bottom 90%, and used their combined powers to do that, then what used to be the bottom 9% suddenly becomes the bottom 90%. Probably those people get really scared that the same will happen to them at the next meeting of the top 10%ers council.
But on the other hand, elites themselves also have hierarchies. There used to be kings, lower nobility, higher nobility, etc. Those would fight all the time about how much power each of them had. If the top 10% of the human population had a secret meeting to kill the bottom 90%, and used their combined powers to do that, then what used to be the bottom 9% suddenly becomes the bottom 90%. Probably those people get really scared that the same will happen to them at the next meeting of the top 10%ers council.