I agree 100% the attack on biimaal by these moryaans was completely unprovoked, Marka has always been biimaal territory for centuries, not only do they shamelessly claim land that doesn't belong to them, but burn, kill and plunder until they get what they want. AUN to all biimals that have passed away due to HG moryanism
The conflict ain't as straightforward as you think. It boils down to the agricultural resources. Unlike the Digil, the Biimaal are more assertive about regaining their farmland that the Kacaan nationalised and the Habargidir later took control of in the mid-90's. The HG do not want to let go of the looted plantations whilst the Biimaal want justice. The battles in Marka town are a side show. In actual fact, AS are indirectly in control of Marka town whilst the Biimaal have focused on consolidating their control on the outer suburbs of Marka where they live in and the surrounding countryside. The only thing stopping them from acquiring full control of Degmada Marka is the unwillingness of the Central Government to fully equip the Biimaal militia due to pressure from Habargidir who do not want to see the natives of Lower Shabelle empowered. The anarchic status-quo benefits HG because if the Rule of Law returns, they will lose the Xaram gains they made during the chaos of the Civil War. Hence, why they flirt with AS whilst also forming the bulk of the SNA stationed in Lower Shabelle.