Galbeedi,
Jaal Marroo had an opportunity to lay down arms and be granted a cushy job within Oromia or by the Federal Government. He was one of the first to see through Abiy's duplicity. I can't speak to his leadership style but he does have following and has successfully fought off the government. The war in Oromia was hidden one
The today's OLA is different in that it is mostly students, not peasants led by few educated men. Its ranks have filled and they pretty much control the vast countryside.
OLA have loyalties in the huge Oromia state security. Once Abiy is gone, this group will quickly switch sides. A lot of them already have.
The TPLF and Tigrians have an existential question to ask, try to rule Ethiopia with iron fist and risk another threat to their homeland or set the stage for dissolution of Ethiopia in a way that favors them?
Any alliances they have now is temporary. All groups will turn on each other.
Three men are important to the Oromo, Jawar who represents Muslims by default, Lemma who Abiy stabbed in the back, and Jaal Marroo. They are all young men who are avowed nationalists. They don't trust TPLF nor they want to be junior partners.
In fact, I think Somalis have to worry more about Oromos. TPLF is concerned about Amharas and Eritrea.