Complex sentence: During the nineteenth and twentieth centuries some of the most successful social entrepreneurs effectively straddled the civic, governmental, and business worlds--promoting ideas that were taken up by mainstream public services in welfare, schools, and health care.
Split into simpler sentences: During the nineteenth and twentieth centuries some of the most successful social entrepreneurs effectively straddled the civic, governmental, and business worlds. Such pioneers promoted ideas that were taken up by mainstream public services in welfare, schools, and health care.