People noticed the disciples were swiping the ass. They did as they were told. When questioned as to why they were taking the ass, they said as they were told and were allowed to take it. They brought it back to Jesus. Put there cloaks on its back to make for a more comfortable ride for Jesus and the parade now was staged and ready to proceed to Jerusalem.
People react in a funny way to a parade.
Some just sit and watch. Others want to actively participate. Did you ever see the little boys riding their bicycles all along the parade route. The venders with the balloons and toys. All want to be part of the action when a parade comes to town.