Complex sentence: He entered publishing upon recognizing the new way comics were being distributed--that there was an opening for a new, smaller publisher and that the advent of the Macintosh computer (circa 1986) allowed a small company to look bigger.
Split into simpler sentences: He entered publishing upon recognizing the new way comics were being distributed--and that there was an opening for new, smaller publisher. And that the advent of the Macintosh computer (circa 1986) allowed a small company to look bigger.