Affordable, efficient, reliable and effective video surveillance tech hasn't really been around for very long, and argiculture isn't exactly silicon valley, the people in charge aren't always very enthusiastic about embracing new technologies. I find it quite easy to believe that an owner of a dairy business might do periodic in-person audits of employees and feel that that's sufficient.
Additionally, Idaho is known for its libertarian attitudes, and around-the-clock video surveillance of the entire premises is quite at odds with those ideals. I don't find it hard to imagine that an agricultural operation with video surveillance is meaningfully less attractive to employees.
And finally, how bad are the attrocities in these videos relative to the conditions that animals are normally kept in? They can get pretty bad, but I don't think there's an order of magnitude of difference. How much worse is it to be beaten when you already live your life in a cage sitting in your own filth? If you are utterly disgusted by the abuse revealed in these videos, can you really justify modern livestock farming at all? Either you accept that we should treat animals as objects, as we are evolutionarily prepared to do, or you can argue that because we now have the infrastructure available to us to treat animals with respect, we have the responsibility to do so. You can choose a position somewhere along that spectrum, but if you draw the line between imprisoning animals in unliveable conditions so unhealthy that they are fed antibiotics to prevent the spread of disease, and beating them, then I'd argue that the level of precision of your position on the animal rights spectrum is irrationally high, and that it cannot be based in logic.