PowerPoint was an acquisition, though Microsoft had considered building a competitor in house like Word and Excel.

I found Robert Gaskin's fascinating book on the history of PowerPoint and its acquisition by Microsoft in an HN comment a few weeks back and it's a fascinating read of that fascinating paradigm shift in productivity apps that happened in the mid-to-late 1980s (that Microsoft was able to play a hot hand in):

http://www.robertgaskins.com/powerpoint-history/sweating-bul...