I am an avid Legend of Zelda fan. And one prevalent theory is that of the split timelines. One day as I was watching an old DBZK episode with Future Trunks in it, I realized how much his meddling in time could have ushered in multiple timelines in which different events occur. I've seen many people saying how other villains could have come and concurred Earth because the Z fighters were not there to fight back. (Though the list of villains are minute because most are caused by the Z-fighters interference or presence, such as Cell, Buu, Cooler, Bojack etc.) But think more clearly about this; every action conceives a separate universe, each with its own outcome, some leading to other universes. This is why Android 16 appeared in the main DBZ universe, when he did not in Future Trunk's. This also explains how Androids 17 and 18 are also stronger for reasons unknown.
The factors that could have influenced the outcome of the Android/Cell saga include:
- The victory/loss of the Z fighters
- The amount of interference by Future Trunks
- Interference by other villains (including Cell)
- The signifance of the Z fighters in the schemes of the other villians
- Future Gohan's and Bulma's actions
- The Androids' actions
The second, third and last one seem to have the most impact. Future Trunks was not meant to fight Mecha Frieza. The Z Fighters were not meant to know about the Android's assault beforehand. Goku was not meant to have that medicine. The Z Fighters were not meant to be prepared. Cell was not meant to interfer. Trunks wasn't meant to die. Krillin was not meant to hesitate when he had the chance to deactivate the Androids.
Future Trunks sole existence in a time before his adolesence happened ignited a plethora of events not meant to happen. Android 16 is proof of this.
Any event happening between Dragon Ball and Dragon Ball Z could have influenced the strength of the Androids. Think about it. What if Goku had meddled further in the main timeline than in Trunk's? Dr. Gero would have delved further in his quest to eliminate him. Any slight variation in the plot could have changed anything. Even which Androids Dr. Gero would have deployed or created.
Concerning Trunk's sword, there are several theories to that. It is possible that the sword used by Gohan in early Dragon Ball Z could have been handed down to a young Future Trunks. It is possible that Tapion could have existed on Earth prior to his known debut. A possible wish by the dragon balls before they disappeared? Perhaps in their timeline Tapion died a true hero instead of being trapped within a music box. A simple "I wish a great hero can come save us." Could have sufficed. But it's a stretch. Nevertheless there has to be some reason Future Trunks could have obtained that sword without travelling through time. Give me your opinion.