I agree that he ought to be disqualified from holding office per the 14th Amendment, however I doubt it will apply.

U.S. Const. amend. XIV, § 3:

No person shall be a Senator or Representative in Congress, or elector of President and Vice-President, or hold any office, civil or military, under the United States, or under any State, who, having previously taken an oath, as a member of Congress, or as an officer of the United States, or as a member of any State legislature, or as an executive or judicial officer of any State, to support the Constitution of the United States, shall have engaged in insurrection or rebellion against the same, or given aid or comfort to the enemies thereof. But Congress may by a vote of two-thirds of each House, remove such disability.

I've bolded the parts which might apply to Trump.

executive or judicial officer of any State

He was an Executive, but not of any State, so he doesn't meet that condition.

officer of the United States

"Officer of the United States" has an established meaning in the constitution as, essentially, "officers appointed by the President" (with approval from the Senate).

U.S. Const. art. II, § 2, cl. 2:

He 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.

If we take this list to be exhaustive, then Officers must be appointed by the President and are not elected by the public, therefore the President himself is excluded from the definition of "Officers of the United States".

The Supreme Court has followed this reasoning in the past.

United States v. Mouat, 124 U.S. 303 (1888)

Unless a person in the service of the government, therefore, holds his place by virtue of an appointment by the President or of one of the courts of justice or heads of departments authorized by law to make such an appointment, he is not, strictly speaking, an officer of the United States.

And Justice Roberts has used this reasoning more recently.

Free Enterprise Fund v. Public Company Accounting Oversight Bd., 561 U.S. 477 (2010):

The diffusion of power carries with it a diffusion of accountability. The people do not vote for the “Officers of the United States.” Art. II, §2, cl. 2. They instead look to the President to guide the “assistants or deputies … subject to his superintendence.”

And finally

having previously taken an oath

The oath taken by those Congress and Officers of the United States (and all others listed in U.S. Const. amend. XIV, § 3) is a different oath to the one sworn by the President, and it may be argued that the oath U.S. Const. amend. XIV refers to is explicitly that sworn by members of Congress and other Officers, not the Presidential Oath of Office. (Although this to me is the weakest part of the arguement.)

While I completely agree that by any reasonable standard Trump ought to be disqualified from holding office per the 14th Amendment, it is unfortunately not a reasonable standard that he will be held to. It is this Supreme Court's standard.