I actually made a small essay about this topic. It’s not my best defense, but it’s a reason at least.
It’s quite likely that he knew what was going to happen long before he gave magic to humanity. I imagine he has some plan that we don’t know about yet. Perhaps he wanted humanity to rise above the gods? I don’t know, but since he does have foresight it’s likely he had/has a carefully laid out plan and has already seen all that the AU contains. There’s also the fact that Titans and gods don’t truly die so he may be planning some grand return. Though this may have been delayed by Acheron reviving his body. Overall I think given his mythological precedent his gifting magic to humanity was a bid to make humanity greater than the Olympians.