Some people argue that Trump cannot be disqualified unless he has been convicted of some form of insurrection, but the 14th amendment was passed after President Andrew Johnson had already pardoned former Confederacy officeholders of their criminal participation in rebellion. The problem was that Southern voters were electing to office those who had rebelled against Constitutional law. These were mainly, like President Johnson, Democrats. The Democratic Party was more sympathetic to the Confederate cause, so their candidates were more likely to have been popular supporters of the rebellion. The 14th amendment nevertheless disqualified them from running for public office.
Ironically, the party most threatened by 14th amendment restrictions today is the Republican Party--the same party that promoted adoption of the 14th amendment. It is pretty clear that the original intent of the framers of the amendment was to disqualify candidates who had violated their oath to support the Constitution. Donald Trump had very clearly violated his oath of office, being the first President to mount a resistance to the peaceful transfer of power to the winner of a presidential election. However, that doesn't mean that the Republican-dominated Supreme Court is going to deny him a mulligan on taking that oath of office again.