[not2b]

But you'd have to cram so many levels logic into that single cycle that you'd have to decrease the clock frequency to meet timing constraints, meaning that code that is not dominated by division would slow down. And a multi-cycle division can often happen in parallel with other operations.

[rcxdude]

If you simply try to take a design and make it take a single cycle while using the same area, yes. But usually you can trade off area (and power) for latency, by essentially having redundant logic throughout the operation. That's the point being made: the CPU manufacturers don't really consider it worth pushing this tradeoff (which is often quite non-linear).