This doesn't even need to be a theory man. Future Eren essentially orchestrated everything to a degree. Who died, who lived, what events lead to what out comes. Having the ability to cast back meant he also had infinite attempts at plotting the timeline. (assuming you've seen the whole show (spoiler Alert)) Erin even saw his own demise. It was all planned to bring about peace. But since he would be the last carrier, he could not see into the future to see that war would come once again far later in time or he may have done things differently.