Complex sentence: K-tel eventually expanded to serve 34 national markets, and after a very successful 1970s, the company heavily invested in real estate, oil and gas exploration, films and video games in the early 80's.
Split into simpler sentences: K-tel eventually expanded to serve 34 national markets. After a very successful 1970s, the company heavily invested in real estate, oil and gas exploration, films and video games in the early 80's.