Complex sentence: Costa e Silva and Médici reversed the free market reforms previously established, and re-affirmed the developmentalist trend that had prevailed in the South American country during most of the period from 1930 until the 1964 coup.
Split into simpler sentences: Costa e Silva and Médici reversed the free market reforms previously established. They re-affirmed the national developmentalist trend that had prevailed in the South American country during most of the period from 1930 until the 1964 coup.