Apparently the subpoena was issued weeks ago, and documents have been flowing.
Exclusive: The special counsel has subpoenaed Trump Organization records, some related to Russia, bringing the inquiry closer to the president https://t.co/Gi9JexvR4O— The New York Times (@nytimes) March 15, 2018
As for a possible subtext:
Senior congressional source says that Mueller beginning with a subpoena, rather than typical document request, suggests special counsel intends to put every Trump Org staffer on alert not to destroy evidence.— Ari Melber (@AriMelber) March 15, 2018
Meanwhile, un-indicted co- conspirator Donald "Rump" Trump's Kitchen Cabinet is urging action.