I dug up the original article: https://www.politico.com/magazine/story/2018/03/09/bitcoin-mining-energy-prices-smalltown-feature-217230/
In this case, they already were exporting 80% of the hydro-energy generated, about enough to power Los Angeles in 2018 when it was written. Maybe there are some cases for your suggestion on a small scale, but if a site is generating enough excess electricity to make mining worthwhile, why would it be less worthwhile to connect it to a larger grid?
I’ll concede there’s probably something to miners footing the initial capital to build the infrastructure, and if it’s in a remote area it may be prohibitively expensive for public utilities to extend the grid to it. But mining setups still require high internet speed connections to use the network, and I just have to wonder if installing that is a better use of resources than installing power lines to take some load off non-renewable power sources.