Right, but taxing a CPU, PC Bus, and PC memory takes more electricity than doing the same amount of "work" on a GPU with longer, more specialized pathways, allowing more work on a single cycle, but less flexibility on the type of work. So if it takes 1hr fully taxing a CPU, PC bus, etc, vs 1 hour fully taxing a GPU and its integrated memory and bus, the one using the GPU is going to take more electricity. Also, you can chain GPUs which can't be done the same with CPUs since GPUs all have their own discrete bus and memory on a single card. Problem became that GPU production couldn't keep up with demand so they became more expensive for the hardware, but overall, the cost of electricity vs value of the blocks combined with producing fewer blocks on a CPU once the chains reach a similar complexity as a competing cryptocurrency, means that overall you're more likely to make more profit from GPU based mining than CPU based mining.

It's a complex calculation to figure out and many people mine without realizing the money they're spending on electricity, home cooling, and parts wear is more than they're making on the crypyo.