Yeah, I was thinking the same. In a big enough company, you can spend 3-6 months "onboarding" while drawing a paycheck and not having to do enough to get found out as a fraud. Even after the onboarding period, a skilled fraudster might find a way to blend in and hide if the circumstances are right. Or the company might have a policy (from legal) not to just fire people on the spot, but instead put them on a PIP and/or collect months of documentation of poor performance before doing letting them go.

Even if they fail to last, they've still been drawing a paycheck for maybe 3-6 months (or more?), and that might be an acceptable "win".