Complex sentence: He disappointed the crowd somewhat by calling the revolution a chance to continue the work he had started 20 years earlier, and prune out what was wrong with Communism; by that time the demonstrators in Prague wanted nothing to do with Communism of any sort.
Split into simpler sentences: He disappointed the crowd somewhat by calling the revolution a chance to continue the work he started 20 years earlier and prune out what was wrong with Communism. By this time, however, the demonstrators in Prague wanted nothing to do with Communism of any sort.