Aim wrote: Fri Oct 01, 2021 8:41 pm
Is it ever confirmed that the reason he didn’t get erased from the future was because he was immortal? I don’t think that was ever the case, like, Trunks wouldn’t just disappear if his present self wasn’t born, they are separate timelines.
Yes. Zamasu's immortality always protected him from erasure.
As directly stated by Beerus, not even a Destroyer's Hakai can harm Zamasu, which means that not even the strongest Saiyans (Vegito, Goku, Vegeta, Trunks...) could kill him. This is why in the new Future timeline create at the point before Black and Zamasu attack, Whis will use his Angel powers to seal Immortal Zamasu. Because not even Lord Beerus' Hakai can destroy an Immortal being like Zamasu.
When Zamasu's spirit merges with the Cosmos, it is directly stated that this was possible thanks to Super Shenron's power, which allowed Zamasu's spirit to remain in the living world even after the destruction of his physical body.
The other Zamasu, Goku Black, wasn't protected by Immortality though, he was protected by the Time Ring. The Time Ring protected him from anything that happened in the Time-Space continuum, which is why he didn't cease to exist when Beerus destroyed Present Zamasu (his counterpart).
At his core Zamasu is good like Shin, though I guess you could say he was so fastidious that it backfired. But you know, for this "Future Trunks Arc" you had to depict Zamasu and Trunks' inner conflict, right? If this was back when I was drawing the manga myself then I doubt if I could have done it. I mean, I'm not very good at depicting the characters' psychology on the page. So this all came together because now I only have to think up the story. [...] On my own, I doubt I would have been able to express Zamasu's fall to the dark side.
Akira Toriyama, DBS vol.4 joint interview with Toyotaro