I believe Charles Widmore was ejected from the island during the Dharma period for some unknown transgression and is trying to change the time-line of the Island in order to return and take over leadership there. When Ben's group states that they will cease to exist if the proper timeline gets altered, they are referring to themselves, not everyone on the planet.
During the time leaps by the losties, young Widmore found out that Desmond is "special" and can change the timeline of the events on the Island. He was present as a young man when the H bomb was buried and the hatch was built around it. Through a series of manipulations, (getting Libby to give Des a boat out of nowhere etc.) he arranged for Desmond to land on the Island and become the sole caretaker of the hatch.
Widmore owns Oceanic and can order his employees to do as he wants as demonstrated when he waylaid Sun at the airport. He was able to divert Oceanic 815 to fly over the Island to coincide with the time when he knew Desmond would fail to input the numbers and cause the event that crashed the plane. Perhaps he knew Lapidus would not follow these orders and arranged for the substitute pilot.
Theory by Tanyam
During the time leaps by the losties, young Widmore found out that Desmond is "special" and can change the timeline of the events on the Island. He was present as a young man when the H bomb was buried and the hatch was built around it. Through a series of manipulations, (getting Libby to give Des a boat out of nowhere etc.) he arranged for Desmond to land on the Island and become the sole caretaker of the hatch.
Widmore owns Oceanic and can order his employees to do as he wants as demonstrated when he waylaid Sun at the airport. He was able to divert Oceanic 815 to fly over the Island to coincide with the time when he knew Desmond would fail to input the numbers and cause the event that crashed the plane. Perhaps he knew Lapidus would not follow these orders and arranged for the substitute pilot.
Theory by Tanyam
