[phire]

We are only talking about "fast" relative to normal planetary timescales.

My understanding is that it would still take hundreds of years for the solar wind to strip away the atmosphere. If a civilisation had the technology to quickly put an atmosphere on the moon, it has the technology to continually replenish the atmosphere as long as that civilisation lasts.

It would never be practical (or a good idea) but a post-scarcity society could pull it off as a vanity project.