Complex sentence: The PSI looked like the driving force behind the bulk of reforms initiated by the Pentapartito, but Craxi lost his post in March 1987 due to a conflict with the other parties of the coalition over the proposed budget for 1987.
Split into simpler sentences: The PSI looked like the driving force behind the bulk of reforms initiated by the "Pentapartito". Craxi, however, lost his post in March 1987 due to a conflict with the other parties of the coalition over the proposed budget for 1987.