As mentioned elsewhere, its a combination of factors at least for here in Provo. Provo does have a sizable number of tech startups like LucidChart and according to this report it was number 11 on the tech startup list http://www.heraldextra.com/news/local/moving-up-provo-orem-a...
Also, as part of the deal for coming to Provo, Provo city sold the existing fiber network to google for a single dollar and google's job was to upgrade the system to gigabit. The whole infrastructure was in place for the most part, so it was a good deal that they couldn't pass up. http://www.tomshardware.com/news/Google-Fiber-Provo-iProvo-P...