There was a really good episode of the Odd Lots podcast where they discussed this. Arizona is a very favorable location for semiconductor fabs because there's a very low risk for natural disaster (no hurricanes or earthquakes), the temperature changes are relatively predictable, land and electricity are relatively cheap, and Intel already has a large fab there. Water is a little bit of a struggle, but they can buy water rights from farmers, who use most of Arizona's water.

It's dry, weather is consistent(though hot), has a robust power grid, has an engineering school who produces semiconductor grads, has a large pre-existing industrial base and has ready access to water (the plant is literally next to a 340 mile water canal that runs from the Colorado river and sits atop a water basin that has had water levels rising since the 80s).

I'm not sure there are many better places outside Oregon, California or Texas...

As others have mentioned there is a large Intel fab (and other smaller fabs) in the area. I suspect this gives them insights into the feasibility of success there and also means there is an existing talent pool to draw from. It basically de-risks the investment. There are probably only a handful of likely places to do this - OR, CA, AZ, TX, maybe NY. Intel building in OH is more difficult from a bootstraping perspective.

Arizona has a low chance of natural disasters, land is relatively cheap, and they're known for being tax competitive.