It's a number of things.
The vast amounts of hydo power and colder climate are a big plus.
Next is as mentioned in the article there are a lot of empty facilities that already had a large amount of the infrastructure in place.
Not having to build a facility but rather just leasing and doing some changes / upgrades to an existing one saves a ton of money and time.
And no matter what, being close to the money people always helps.
They are not neighbors, New Mexico is in the way :-)
Texas has been giving massive tax incentives to companies to move there and due to the way the power is sold in Texas it is a good deal for miners:
From:
https://www.washingtonpost.com/technology/2021/07/08/bitcoin-mining-texas-electricity/But thanks to the way Texas power companies deal with large electricity customers like Whinstone, Harris’s bitcoin mine, one of the few owned by a publicly traded company, didn’t suffer. Instead, the state’s electricity operator, the Electric Reliability Council of Texas (ERCOT), began to pay Whinstone — for having agreed to quit buying power amid heightened demand.
And
During the days-long blackout that crippled Texas in February, bitcoin mines completely went offline. ERCOT paid the companies for doing so.
So yeah, it's a good deal since the people of Texas get to pay them for mining losses when things go wrong.
-Dave