I was going to say exactly this - Word had very little competition, whereas GitHub has many equivalent competitors. I'm a fan of BitBucket - they allow free private repos, but the company as a whole offers multiple other enterprise solutions above and beyond what GitHub provides.
Word had massive amounts of competition. WordPerfect dominated the market well before Microsoft Word, was the biggest competitor for a long time, and still remains popular in niche applications. Lotus Word Pro, WordStar, StarOffice, and countless other lesser used products.
Arguably, word processors are the one piece of software that probably has had the most competition throughout the years.
WordPerfect is still being used widely in the legal fields. StarOffice was open sourced and became OpenOffice and more recently has been forked into LibreOffice. Since we're now talking about more modern competition there's also Google Docs and iWork (for Mac only). All of these word processors are very widely used.
Either way, you were making the claim that Microsoft Word had very little competition, while GitHub has overwhelming competition. This is very far from the truth. Microsoft Word has and has always had very healthy competition in much the same way that GitHub has plenty of competition. Like it or not, at this point in time GitHub is the golden standard, while the competition is riding in their coattails. Very similar to Microsoft Word.
