This has probably been said before but I wanted to see what people thought. In the OT it seems that many of the characters that were not skipping through time such as Widmore, Eloise, Richard, Jacob,... have all been living their lives to make sure their past ended up the same way. This means that they must make sure everyone that was on the island must stay on the island. Who knows that could be why Ben is always so adamant on keeping Juliet and the others on the island and by the kidnappings. Now what about the FST being the lives of those people who didn't have to do this. They have no knowledge of the losties coming to the island because it never happened. Therefore everything they do is not to get the losties to the island and skip through time. Example, Widmore is horrible to Desmond in the OT because he knows Desmond must go to the island to not push the button at the exact moment the losties are flying over. If Widmore was a normal guy he would probably give his blessing to Penny and Desmond and they would be married when they were supposed to.
I guess I am just saying that the FST is a timeline where there is absolutely, NO time travel. If this is the case there is no way the Jughead was set off by the Losties so they are not the cause of the Island sinking. Of course without time travel, Daniel wouldn't be able to go back to the 50's and tell them to bury the bomb so it could have still gone off, but I doubt that. One other thing I think about are the theories that some characters are actually someone from the future. Like Aaron is jacob and so on. If some of these Theories hold true, Without Time Travel these people would not exist. That could also be the reason the island sunk because there is no Jacob or MIB. I hope I didnt confuse the heck out of everyone I kinda had one idea and it led to many others. Thanks