This was my first thought, but it doesn’t work too well if you think about how government actually works, which is hierarchical. The President is able to give orders directly to a few handfuls of people, who can then decide to carry out or not carry out the orders they receive. If that order is “tell everyone in your department to stop working”, there’s a chance that they simply don’t think it’s a good idea, and will refuse to pass along the order. This is why Nixon went through multiple AGs to get someone to fire the special prosecutor.
If the funding isn’t there, then the reason government employees wouldn’t work is that they wouldn’t get paid. Only ones that are in very specific jobs with public safety directly at risk would likely be willing to work without pay - and those jobs almost certainly have full funding anyway because of their criticality. To most everyone, it’s just a job, and there’s no point showing up if you’re not getting paid.