Why did agrarian civilizations like the Mongol empire tend to grow? Why was this so Important. (Please don't answer if you don't know)

Agrarian civilizations like the Mongol Empire tended to grow simply because civilization and agriculture are closely related, in fact, civilization only emerged when agriculture became the main form of food supply.

The reason is that agriculture produces more food (not necessarily a better diet) than old nomadic, and semi-nomadic lifestyles. This surplus food could be used then to increase the economic power of the population as a whole, creating what we know as a civilization.

b. germany and italy

one of the main reasons was definitely slavery. back in 1861, republican abraham lincoln was elected and ended up being a major influence in the slavery business. slavery greatly affected the texas economy because back in 1845 during the annexation of texas, slaves became a big part of the texas population. many texans that were in favor of the secession influenced groups through party ties.