Of course they remained 'great pals'. Mr Nice Guy could never not get along with his ex. That would damage his brand.Jim just said in his video that they split up because they became "great pals" and nothing more. And I think that's a fair statement. People fell out of love and keep liking each other as friends, some people stay married and some don't.
I do however agree that growing apart after being together from a young age is understandable, especially compounded by how much their relationship was an intergral factor to their 'joint' careers. Especially for him, the 'Tan and Jim', Mr Husband persona. Tanya was rather safe just doing makeup. Outside factors change and so do hearts. What you wanted five years ago you might not want now.