Still, they are not in the business of pissing off their clients. Marshall isn't as huge as some of Sodexo's contracts, but it is certainly a big enough contract that Aramark or a handful of others are always chomping at the bit to come in and take from a dissatisfied client. Sodexo knows this and will try its best not to allow it to happen. Marshall can put pressure on what it wants from their services and Sodexo will likely comply, as long as it is within reason.
You are merely speculating. Clearly you do not understand P/L accounts and how contracted service companies operate. Marshall has say so in most of what occurs. You're acting like Sodexo is the client when it's the other way around. Now then, if something is not important enough to Marshall to push back when Sodexo approaches its client and says, "we would like to terminate concessions for ______ ," that's an entirely different possibility. Sodexo could have sweetened the pot by saying they will donate towards construction of something, and, in turn, Marshall agrees not to allow certain vendors to continue, that's also a likely scenario on how this happened.