I think a big reason why Gohan was so weak compared to his main timeline counterpart even as a Super Saiyan is because he never got trained properly by Goku. Piccolo helped him a lot, sure, but he needed his father and a fellow Saiyan to show him how to really control his power and ascend to greater heights.

I'm gonna think really in depth about this so bear with me;

In Trunks' timeline, I think they made it so 17/18 successfully killed everyone because Goku wasn't around. It's like a common formula that Dragonball has always followed, where everyone's in trouble until Goku comes in and saves the day however he can. Goku got sick and never even had any chance to meet and fight them, so naturally I think the devastation of Trunks' timeline is what happens when Goku doesn't show up.

I imagine if Goku survived his virus, he would've been defeated too by the Androids but probably would've survived the first encounter and made sure no one got in their way again until they were ready, and thus trained in the HTC like in the main timeline where all the Saiyans became incredibly strong learning to ascend to the next level. Granted, there is the factor that in Trunks' timeline, 17 and 18 weren't awoken abruptly like they were in the main timeline, meaning their programming was probably complete and they felt the need to kill and destroy, where as in the main timeline, with Trunks' warning they met them early where they probably weren't even close to being ready to obey anything Gero programmed into their brains. Consequently, 17 and 18 in Trunks' timeline were bloodthirsty and may have tried to kill them after the first encounter with the Z fighters, unlike in the main timeline where the twins didn't want to kill anyone but rather beat up the Z fighters to show them they're not to be fucked with.