Their main job is helping the sentient beings to escape from samsara thoroughly, rather than for the happiness of all sentient beings in this finite life.
Life aint finite in the method people think.
ie.... you sleep each nite (not conscious) but still alive. You are from the cell division (sperm/egg) of your parents and theirs and theirs and theirs all the way back to the beginning of time.
Darwin, WON! (he lives in what he left)
AS for the possibility, i agree mankind can take metal and make an airplane. To a normal person building a rocketship is practically magic.
In the 1st century, a bic lighter would have made you a god!