How do we get on the moon, why are the sharlayan so sure that they will survive a world ending catastrophe?

If you think it further. They will be part of the story because suddenly they realize that the moon is not save. More than that, it is were all started or we can find information to end it and that's why they help us, bring us to the moon and we fight up there.

If you remember, eureka was also sharlayan, so they are used to build bases everywhere.