They lost the income from the indulgences so of course those running the set-up were not happy. It has an eerie parallel to Jesus in the temple with the money changers.
First, every priest did not abuse Indulgences, only a few did. Secondly, this has nothing to do with the money changers. The idea behind Jesus chasing out the money changers was that the Gentiles were unable to worship God properly in the Temple, as the money changers were set up in the Courtyard of the Gentiles. With all that commotion going on, how could you expect God-fearing Gentiles to praise God properly? Reverant worship has little to do with abuse of Indulgences.
Regards