It flopped because kids did not want to see it, the young audience stayed away in droves.
The film cost $150 Million to produced and made under $35 Million in the USA, it did better at foreign box-office but still came in under the production cost.
I don't think the film was a total disaster as some claim but it did misfire, want to see Peter Pan films that are more fun check out the 2003 Version with Jeremy Sumpter or Hook with Robin Williams. (RIP).
I also think it is time to give these Peter Pan film versions a rest.