This may or may not be the issue, but the situation reminds me of an issue I've been on both sides of.....
I have put together bands many times. Sometimes you'll get someone in who looks like a good fit, and is into what the band is trying to do. But soon after, the guy starts pitching ideas and/or act in a way they are trying to take charge of the band. As the guy who created the vision and put the band together, I have to admit that it rubs me the wrong way when someone else seems like they are taking over. Especially, when it's different than what I envisioned and taking us further from it. I have a friend that I love who is also a great musician, but I can't really do bands with him with me as a leader because of this.
I have also been the guy accused of taking over as well because I take stuff like this seriously. Progress and accomplishment is important to me and my motivation. I was invited to join a band by a friend who was relatively new to the biz and wanted my experience. So, I come in with guns blazing and basically making everyone drink from a firehouse. A day or so later, I get word that my friend was upset by me and that I stole the person's thunder. It was supposed to be his band after all. So, I apologized, became a sideman, and let him do the heavy lifting.
Because of situations like this, I think it's important to state what the leadership of partnership is going to be. It should be explicitly and honestly stated, and shouldn't be implied. It prevents the ruffling of feathers and the ensuing drama that could unfold from it.