Complex sentence: Prior to the collapse Eastern Bloc and breakup of the Soviet Union passenger locomotives used in Russia had been sourced from Czechoslovakia; afterwards these sources were considered too expensive and the Russian state sought to develop indigenous production of passenger rolling stock.
Split into simpler sentences: Prior to the collapse Eastern Bloc and breakup of the Soviet Union passenger locomotives used in Russia had been sourced from Czechoslovakia. After Cold War these sources were considered too expensive and the Russian state sought to develop indigenous production of passenger rolling stock.