That's a bit like asking how the defendant in a legal case is an interested party.
Even if you think someone is guilty, it does make sense to allow them to at least submit their defense. And if they choose to use that time to advocate for their own promotion, let them.
"Stakeholder" literally means someone with a stake in the outcome, which is to say, those who will be affected by the decision. That can include a whole range of people+entities, including citizens (as a group) and the companies to be regulated.
Even if you think someone is guilty, it does make sense to allow them to at least submit their defense. And if they choose to use that time to advocate for their own promotion, let them.