Why did communism fail to connect with nationalism? how did this failure lead to the collapse of the soviet empire?

Communism was captured by a few individuals who controlled the communist party. These leaders did not give heed to the suffering of the majority masses, and were inept,corrupt and oppressive, denying freedoms and liberty.  The majority of the masses thus stopped identifying with the state.

The soviet union populace were living in very disheartening conditions as the leaders pursued military adventures.  The country was impoverished and the people were yearning for freedoms, and when Gorbachev instituted reforms, the people were in need of more.