Even if that's how it ended up, I doubt that was the plan. I think a lot of Google products, especially those from 10+ years ago, start out built for people like themselves: highly tech literate software engineers. As long as that is true enough, extensions are great and useful, and the users are mostly skeptical/aware enough to avoid installing malware. Now the average chrome user is the same person that filled their IE browser window with banzai buddy toolbars.