[Spoilers] Why Zenos is the most important character moving forward

[Erendis]

Maybe I remember it wrong but wasnt this the plan that Thancred had before he collapsed? Making sure that the people ask themselves if this is truly Zenos?

It was and Riol proceeded with that plan after Thancred collapsed. And if I remember correctly Maxima confirmed that it was a success when he arrived in Rhalgr's Reach.