Warum waren die Grenzen des georgianischen Gouvernements und des Governorats von Georgia-Imereri innerhalb des russischen Reiches so groß?

Probably something to do with Tbilisi being the capital and center of Caucasus viceroyalty during the empire.

Georgia-imeretia governerate was sort of unorganized administrative entity, newly incorporated. Think of it like louisiana territory.

Over time it was organized and georgian governerates became size slightly larger then modern georgia.

Natural borders of Georgia, that’s all