That assumes "supporting" functions from HR over Accounting to Sales are actually not doing anything at a daily basis...

How many HR employees do you realistically need for a company that is downsizing?

A lot, until the downsizing is done.

Although the US don't seems to have a lot of these 'worker's rights' so I guess I don't really know (/s).

Quiteva few, actually. Downsizing does require a lot of admin work. Once the downsizing happened, well, those downsizing HR folks are the last to be downsized.

how are you actually this naive? Classic HN attitude of thinking every single job that isnt engineering does nothing.

You understand theres tons of underlying systems like payroll, insurance, legal issues, severance packages, government filings that happen when you either hire or fire someone?

It depends.

Many people would call Amazon a tech company - but they employ a lot of customer service folks, warehouse workers, and delivery drivers. Most people would call Facebook a tech company - but they employ a lot of content moderators and ad sales people. And so on. Most people would call Apple a tech company - but they have people staffing their retail stores and repairing broken laptops. And so on.

Not every business can be run like Google, with zero customer support and zero service delivery :)

And the consensus was that Twitter wouldn't survive the next weekend.

As Microsoft's old lay offs from the Windows team had shown, the company can just keep producing a crappier product and things will just carry on.