Complex sentence: The group was dormant until 2008 when it first raised claims that Mombasa should secede from Kenya to become an independent state, their reason being that the secession would liberate the people of the coast province from marginalization by the successive governments in Kenya.
Split into simpler sentences: The group was dormant until in 2008 when it first raised claims that Mombasa should secede from Kenya to become an independent state. Their reason being that the secession would liberate the people of the coast province from marginalization by the successive governments in Kenya.