"The developers" do not exist. You mean the core project which has it's own developers. Their work may be adopted, but that is a consensus issue and is not their decision. Anyone with an idea to improve bitcoin is welcome to write code and let the bitcoin community make their choice about it's merit. So for me there is no conflict of interest because they do not represent bitcoin, they only represent themselves.
Those who work for Blockstream can effectively block any proposal that does not benefit their interests. Or at least make it very significantly more difficult to get said proposal to get adopted. This effectively gives users the choice between the status quo and what those who work for Blockstream proposes. If the status quo is not what the community wants (like as is the case currently), then the community has little choice other than adopt what Blockstream wants.
