What did they expect? They created the beast themselves. By providing FP+ for a Meet & Greet, then limiting the amount of time the characters are there versus the normal park hours, of course people who are desperate to meet them at the one location they're available are going to all try to get there as early as possible. The IDEAL solution would have been to just hire more friends for Anna and Elsa and provide a M&G location for them at each park (except DAK). Is it not in keeping with good show? Sure. But compared to this alternative I would be willing to suspend disbelief.