You are perfectly right, this has been similar to the "space industry" (which includes 'ballistic nukes' knowhow maintainance). The thing with a bigger collider is it seems there are, not that honnest, scientists retro-fitting models in order to reach 'appropriate for this new collider' energy ranges where 'new physics' could be found.

What does that even mean? The FCC is essentially the next plausible energy range we can probe with a collider.

Going larger would cost more, and add risk.

So like, yes? The obvious thing to do is to analyze our models and come up with experiments to do within energy ranges which are plausibly accessible with near future technology.