I don’t even think Jaffe really understood Kratos, despite creating him. Or rather, he doesn’t seem to understand how he created the fertile ground for this kind of character development arc.
He was always a warrior, but he had a very human element since day one. He had a chance to protect his family again in God of War I and Ares took them away… Again. He knows he can’t get them back and moved forward as the new God of War. Fast forward, the Gods betrayed him (though he was still sympathetic to Athena at the time). Eventually, he waged war with Olympus.
He was part of the pantheon and that would’ve been the entirety of his story arc where he oversaw war for all time.
But the truth this, Kratos has changed, but he largely remained the same. His two constants were always pride in his family and revenge against those who have wronged him. You take those two together (a threat to his family and Gods looking to kill him) and the direction he’s taken is pretty congruent with who Kratos always has been. I guess you can say Kratos would just be a merciless monster for the sake of it, but the old games never explore present aspects of the character (e.g., what kind of father Kratos was). We got a look at that, and with a boy, no less.
I find the franchise did well to age with the audience. I was an angry teen when the original came out. Now I’m kinda mellowed out with a family and I just get it.
I think it did an excellent job of connecting with the audience as we grew up. It’s a bit like Toy Story in that regard.
