ITAR has limits on processing power that can be exported: supercomputers have "dual use" and can be used for military applications, such as simulating nuclear explosions or designing hypersonic weaponry, e.t.c.

Parent poster likely worked for a US company that was doing a customer upgrade abroad (i.e. exporting US technology) that would have tipped the cluster compute capacity above the permissible limits, unless some older nodes were decommissioned and destroyed.