According to Dragon Ball super episode 53, Goku, Beerus and Whis visit Universe 10, where goku has a fight with Kaioshin Zamasu. After their fight zamasu hatred towards humans increase much more and also he comes to know about Time rings, which he had no idea. His hatred towards humans, especially Goku caused for the creation of Goku Black
So therefore trunks coming to past, made goku meet zamasu indirectly trigerring the creation of Goku Black. Therefore creating a time loop
Is my suspicion correct?