LOL. No the diplomats are not the ones who determine US foreign policy. They implement it. No doubt those expelled will be intelligence and military related diplomats. They will be replaced. Those that are PNG'd will go back to postings with their agencies.
The bad part about being PNG'd is that you have only 72 hours to get out of the country. The dependents and the Embassy are stuck with the logistics of shipping their effects out, paying bills, and terminating leases.
This is in retaliation for the “election having”. Thirteen page report released called grizzly steppe
https://www.us-cert.gov/security-publications/GRIZZLY-STEPPE-Russian-Malicious-Cyber-Activity