According to the same site, 43.2% of sites surveyed are running Wordpress. That's over half the PHP number, and I suspect much of the rest is running something

According to the same site, 43.2% of sites surveyed are running Wordpress. That's over half the PHP number, and I suspect much of the rest is running something open source that hasn't been significantly modified by the site operator. I just put up a site running Wordpress. Backend language was not a significant factor in selecting that software. Its ease of deployment on cheap shared hosting was certainly a factor in its initial success.