How can we connect the fifth installment with the previous games in the series?

I liked it. I'm just curious how Sandro can cooperate, for example, with Yog and others who opposed him. And why Enroth, and not Erathia Jadame? After all, Enroth is not a world, but just a country on the planet XEEN. And by the way (I remembered), Enroth is the world of the second game.