No, he was going to destroy the earth, and kill everything in the universe. That was his purpose, which was beyond stupid, as there was no way he should have actually ended up as he did. Besides the need for killing GokuI already said that he lacked a purpose beyond beating Goku, but he happened to do it earlier than the length of the Arc. If the arc was about Goku conclusively then it would have ended at the Instant Kamehameha without Cell actually completing that universal goal of wanting to kill Goku. There really wouldn't have been anything for Cell to do. The same thing happened to No. 17 & 18, where their mission was to kill Goku but they awoke when he was either dead or dying so they had nothing to do and they made it painfully obvious.
No, he was absolutely going to destroy the earth, if they lost, or didn't show up. Nothing in the narrative ever threw what he said into doubt, yeah he wanted to fight Goku. But after that he was going to destroy the planet. Which makesHis priority wasn't to destroy the Earth, it was a condition he set for them to fight him. It was a stake he set. His real purpose was to fight Goku but if Goku wasn't ready he saw no point. So thus he waited. As a Saiyan he wanted Goku to be at his best regardless.
Its the boot strap paradox http://thequantumtunnel.com/continuum-b ... p-paradox/. No the reason why Zamasu became like he did, was because he originally believed the mortals to be dangerous, was humiliated by Goku, but that wasn't the actual catalyst for his change when Gowasu took him to a planet full of mortals, the Babarians, they were a race of monster's, who only destroyed, Gowasu went a thousand years into the future. The Babarians were only a bit more technologically advanced, but still just as violent. That's what comfirmend, at least in Zamasu's eyes that the mortals were all evil, and deserved to be destroyed.That wouldn't explain why Goku black existed then, and the only reason they met Zamasu was because they were seeking out Goku black's origin. Goku then spontaneously wanted to spar with him and he agreed. Goku also didn't actually curb stomp him. He just didn't realize Goku was that strong. There is no reason for that Zamasu to hate mortals solely on one sparing match. What correlation is there for his beliefs if he agreed to spar with Goku? That would make even less sense. It was a trivial fight. If that was the cause then they could easily reverse that and prevent it thus ending the entire arc instantly.
No. It is easier to understand within the Cell arc ignoring the one plothole. The Zamasu arc doesn't make any sense with the logic within it by rewriting the rules entirely.
