What happens, the queens put off a scent, pheromone, that is their scent. The hive learns that scent and it is the queen bee they accept. That scent is what keeps the hive together, drives its aggression or gentleness. When you replace a queen the hive needs to learn the new scent to accept her. If you just toss her in they will kill her even if queenless.
When they are shipped we had 4 queens in the box, it appeared that each queen had a small cluster of bees that stayed around their cage, the other bees were more for warmth mass. It is cold here, cold shipping so xx bees were needed to keep the queens warm. The small group did the feeding of the queens.
Now we pull them out of the box away from this small amount of bees taking care of them, put them in a hive with around 30000+/- bees that need to learn their scent. So she is in a cage until they chew her out. Usually by the time they chew her out, sugar plug, they have learned and accept her scent, it can fail and we have to start all over again.
There is only one queen in a hive at one time, if more, only the strongest survives.
I am queen in our hive! .......................lol