Their stated reason is: "Along with the cameras being used to reduce crime, the sheriff’s office said they may also be used for public safety concerns, including AMBER Alerts and Silver Alerts."
The cameras are good when we're all on the happy path, but as soon as a bad actor gets involved, all of that surveillance won't look so great. History shows that the odds of that happening are decidedly non-zero.
EDIT: Searching for some info on the grant referenced in the article, it appears that a county must match 20% of the grant amount; one example is [1]. I'm sure this looks like a great deal to county officials.
[0] https://www.ketk.com/news/crime-public-safety/new-traffic-ca...