Time Travel is the MIB's Domain by tez360

The MIB believes that humanity always destroys itself. Previous 'group' interactions have supported this theory---the Hostiles vs the US Army, Dharma vs the Hostiles, the breakup of Danielle's group, etc. Jacob believes the opposite---that different 'tribes' of people can come together peacefully on the Island. I think the Losties' arrival on the Island symbolized Jacob's 'victory' over the MIB, and that's why the time travel shenanigans began.

Richard is Jacob's servant, and he's been that for a very long time. Yet Richard didn't know about time travel until he met our guys in the '50s. Presumably, then, time travel is not Jacob's domain; what power governs it then? The MIB.

The time traveling began because the MIB sensed that Jacob was about to win once and for all. Before the Losties arrived, all the groups that formed on the Island were rather psychotically cliquish---the Others and Dharma being prime examples.
The Losties, in contrast, have been extraordinarily welcoming and inclusive: Juliet, Desmond, Daniel, Miles, Charlotte, Frank---all of these started out as strangers and were (relatively quickly) welcomed fully into the group. (Dharma had potential (by welcoming in Sawyer et al) but that potential was squandered through paranoia and self-righteousness.)

By Season 4, Jacob's victory is all but assured. Kate and Sayid, high-ranking members of the beach crew, work with Richard to rescue Ben. Juliet, Alex, and Karl are all hanging with the Losties. Danielle has stopped automatically shooting at people. Ben gets beaten up but nobody bothers shooting him in the head. Daniel, Miles, Charlotte, and Frank are welcomed in. Everybody adores Desmond. While the Losties ostensibly split, they remain together in spirit---Locke and Jack bicker at each other but still inwardly consider themselves part of a single group; they were never going to actually go to war against one another. In fact, Locke's ascension to Island King would potentially have caused all of the fighting to stop, because he would have been in a position to unite the Losties and the Others into one awesome ubergroup (as the writers sort of hinted with Sun---she seemed right at home, hanging with Richard and his crew by the end of Season 5).

The Losties' merger with the Others would have led to a more 'inclusive' membership policy within the overall group, and so the MIB ripped the burgeoning group apart. The main leaders of the Losties were either manipulated off the Island or thrown backwards in time. Eventually, the flashes would have killed off the Losties for good, thus preventing Jacob's overall plan (with the added bonus of upping Dharma's and the Hostiles' paranoia quotients in the past).

He miscalculated the bonds of the group. Locke was willing to leave the Island forever in order to save everybody; Sawyer chose his beach buddies over a quiet life with Dharma; Juliet refused to abandon everybody; Jack and Sawyer beat each other up and then, about ten minutes later, saved each other's lives. Rather than remain in their newly-formed groups (Hurley/Jack/Kate, Sawyer/Juliet/Miles/Jin, Daniel and Sayid off by themselves), they quickly reformed themselves and ran off to change the future. The MIB's plan backfired.
.... Yes this is a LONG theory and not just a question.