It's "infinite monkeys on infinite typewriters" because a million would be far too small a sample size to expect Shakespeare. The monkeys aren't trying to make anything, they're just randomly hitting keys. For Shakespeare to come out, there would likely need to be more Monkeys than there are atoms in the universe. Conversely, we're getting something people enjoy from AI right now. No need to approach infinity. It's not what most people wanted AI to be used for, but it's succeeding at it, and current models have only been around for a few years. This isn't random chance happening upon something we like - this is a pattern-recognizing machine getting progressively better at recognizing the patterns we enjoy.