In Iraq for exemple. At this time, oil was mainly in Kuwait, and Arabs were in Iraq (few oil was discovered). So they created a little country easier to control : Kuwait (in fact this country was created by the brit empire many years before oil usage, for commercial reason, but confirmed at the end of Ottoman empire).
A lot of african borders were drawn in consideration of the transportation lines, to deliver goods to a port. The goal was to control the economy of these countries.
There is a lot of "tactics" for a colonial country to maintain control with very few means. One of them is division, maintain ethnical or religious conflicts. That way, the colonial administration is seen as a good compromise.
But there many other means, like corruption of local elites, false flag operations etc.
Nothing has really changed today.