I think the truth in this point lies in the fact that this was when the British Empire was still around and held large swathes of land with sway over large numbers of people.

That plus the German Empire lost large amounts of land after the great war.

It wasn't insane to pursue land. Not at that time.

The reasons, "science" and supremacism that surrounded it? Yes. Unfortunately, the kind that sweeps a broken, defeated nation under a spell, a mass delusion of grandeur.