Why did Miles and the rest of the goup come to the island for Ben Lineus, and why them?

Well Charles Widmore wanted Ben, so he sent a group of mercenaries to get get him by force even it it meant killing everyone on the island. Miles was there because his abilities were an asset that could help lead them to Ben, Charlotte was probably there because to assist Dan and because of her research on Dharma, and Dan was there to further his research on time and to cure him of the effects his experiments had on him.