I believe that the folks at Mozilla are capable and willing enough to not let an external company interfere with their product in any way that would harm their users. However, it is also a question of being able to communicate this to their users. Putting the logo of a company which is at least not famous for protecting its users right in front of everyone does not help getting this message across. Furthermore, I assume that Mozilla has likely not even received money but just services in-kind. Damaging the reputation of a product that is critical to the open web for a couple of servers?