Question

why do you think it was important for the ruler to control the trade route

Answer 1

if someone came to trade in their kingdom or empire, So, they had to give tax to the king or emperor and the traders sometimes gave gifts to the king or emeror

Answer 2

It was very important for the ruler to control the trade route as it fetched huge income to him. The ruler used to get taxes, gifts and other things from the traders. The ruler used to control the local as well as foreign trade by controlling the trade routes. He used to establish some sort of trade monopoly by controlling these routes.