Complex sentence: In 1936 the Ink Spots became the first African Americans to appear on television; then in 1948 they continued to be television pioneers by becoming the first African Americans to appear on Ed Sullivan's successful TV show.
Split into simpler sentences: In 1936 the Ink Spots became the first African Americans to appear on Television. They also became television pioneers in 1948 by becoming the first African Americans to appear on Ed Sullivan's successful TV show.