And, because it's nuclear, every single one of them has to be reported to the CNSC, lol.
https://www.cnsc-ccsn.gc.ca/eng/act...ilities/event-reporting/nuclear-power-plants/
https://www.opg.com/reporting/regulatory-reporting/event-reports/
And yes, they employ thousands of people. They can do this because nuclear plants generate vast amounts of electricity and so these operating costs are baked into the rates paid for that electricity by ratepayers.
The problem with batteries is that they don't generate electricity, so any operating costs have to be baked into the round-trip costs of the (limited) energy being stored. This is on top of the capital cost that's trying to be paid back.
But even then, with lithium chemistry batteries (particularly Lithium Ion), fires can and do happen, it doesn't matter how much monitoring or how many employees there are. While there are fire suppression systems, once thermal runaway has started, you pretty much just have to let it burn itself out, which is what they did here, and try to prevent it from spreading to neighbouring packs. That's pretty much been the approach with all of these fires. This is why the packs are spaced like they are, to prevent spreading.
This isn't like a power plant where a series of bad things have to happen in order for a major event to occur due to the structure of redundant safeties and containment systems. Lithium ion batteries can, and do, just catch fire, usually caused by a dendrite triggering thermal runaway, and since they provide their own fuel and oxygen, you can't put them out via conventional methods, so it's usually about just pouring tons of water on them (thermal control) to prevent them from spreading while the parts that are currently combusting, use up their fuel.
I'm hopeful we start working on utilizing other chemistries that aren't prone to this issue.