The right of imaamate belongs to the appointed Imaam of the Musjid. Without his consent it is improper for anyone else to step forward even if he may be superior in knowledge, piety, etc.
It is not proper for the mutawallis of the Musjid to overstep the right of the Imaam and usher forward anyone else. When a visiting personality or Aalim comes, the Musjid trustees simply override the appointed Imaam and insist that the visitor leads the Salaat. The mutawallis do not have this right