Presumably a lot of these are content moderation staff, often much cheaper than engineers. Facebook claimed to have made good progress in the last year automating moderation, but could also just be backing off on moderation to reduce costs at increased risk of regulation.

Often that kind of staff will be employed via agencies, so it's difficult to really compare between companies as we don't have the numbers. For instance, Apple presumably need a lot of staff to moderate apple pay, but if they have outsourced the rolls we won't know how many there are or see if they get cut.