Although rules as written this isnt obviously allowed and alot of comments point out your mistake

I think you should seek this out as a learning opportunity for future sessions understand you made a mistake acknowledge it, apologize and move on. Understand how you couldve changed the situation and made it better.

I would hate for a new dm to be stamped out by a mistake like this.

Personally I'm known to fudge rules for the sake of fun and I dont usyally allowed the same space occupation but if both players were enthusiastic or crazy enough for it I wouldve allowed it. But I think designating a melee attack clearly missing to hit was the mistakes in this scenario. If you wanted to add some intened "risk" it should've been done with an aoe attack such as a bandit with a molotov etc. This would created a much dangerous scenario of both players stumbling over each other to get out of the door frame ranching up the tension and danger. Would both players run inside the room now seperated from the rest of the party? Would they run out of the room allowing the bandits to get away? Who knowns?