Of course, there are a lot of things going on. However, I think one important thing is that American workplaces, over the last twenty or more years, gradually accumulated immensely toxic/abusive cultures. At the point of the pandemic, when many people had unemployment/work-at-home/savings, a lot of workers' had their tolerance of that interrupted and then just refused to return.
The thing with the situation is toxic work environments basically are going to double down on their claims, their view of what a sane environment and reasonable pay are. So these organizations are eating through employees and so they'd be the worst customers of a job board. The question how much 70m Record vetted their customers.
Article explaining the toxic angle: https://www.greatplacetowork.com/resources/blog/how-toxic-co...
Employees discuss their views: https://www.reddit.com/r/antiwork/