Complex sentence: Once both goals were realised, the program was subsequently abandoned following the change in Soviet leadership, which was less concerned about stunt and prestige flights, and allowed the Soviet designers to concentrate on the Soyuz programme.
Split into simpler sentences: Once both goals were realised, the program was abandoned. This followed the change in Soviet leadership, which was less concerned about stunt and prestige flights, and allowed the Soviet designers to concentrate on the Soyuz programme.