Complex sentence: The rich province of Katanga, soon followed by the eastern part of Kasai were trying to gain independence, being as rich as they were in copper, cobalt and diamonds, they believed that they would be better off without the rest of Congo.
Split into simpler sentences: The rich province of Katanga, soon followed by the eastern part of Kasai were trying to gain independence. As they were rich in copper, cobalt and diamonds, they believed that they would be better off without the rest of Congo.