This jives with my memory of that time as well. Apache just couldn't keep up with Nginx' async speed, and if you weren't having to deal with PHP (before FastCGI's adoption), there was no real reason to use Apache.
And post-FCGI's adoption, you didn't need to use Apache, so... why use it?
And post-FCGI's adoption, you didn't need to use Apache, so... why use it?