The Senate has to ratify, and at any time during those processes, the Republicans could have shot them down. But they didn’t, with the usual pathetic excuses.
Article Two, Section Two, Paragraph Two of the Constitution grants advice and consent power to the Senate. A president “nominates” but with no Senate consent, there’s no appointment.
Article II, Section 2, Paragraph 2:
[The President] shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur; and he shall NOMINATE, and by and with the Advice and Consent of the Senate, shall appoint Ambassadors, other public Ministers and Consuls, JUDGES OF THE SUPREME COURT, and all other Officers of the United States, whose Appointments are not herein otherwise provided for, and which shall be established by Law: but the Congress may by Law vest the Appointment of such inferior Officers, as they think proper, in the President alone, in the Courts of Law, or in the Heads of Departments.