It isn't, that's the point. Virtually every constitutional arrangement, at the end of the day, is reliant on the public to enforce it. No matter how robust it might be on paper, if the public is apathetic or openly cheering for constitutional norms to be flouted, no piece of paper will stand in the way.
In the US, there are two flaws that would allow that to play out. The first is that SCOTUS has no actual enforcement power: it is reliant on the belief that what SCOTUS says goes, and the assumption that there would be severe consequences for being openly contemptuous of a Supreme Court ruling. If that isn't the case, the Constitution largely ceases to exist overnight.
There is also a more subtle way to approach it: rather than sideline the court, co-opt it. Ensure that it gives a rubber-stamp to all of your decisions, no matter how nakedly unconstitutional. This has long been a favourite of dictators who wanted the sheen of legitimacy, and in the US there is a loophole big enough to move a cruise ship through: the Constitution defines the role of the Supreme Court, but it doesn't define its size. Over the decades this has led to musing (much of it on the left, actually) about court-packing, whereby you would greatly increase the number of sitting justices in order to reshape its partisan lean. If a wannabe dictator had a bare majority in the House and Senate, in addition to the presidency, it's totally constitutional to pass a bill increasing the number of justices on the Supreme Court from 9 to 19, and then seating 10 lackeys. And because SCOTUS is the arbiter of constitutionality, it's totally cool when those 10 lackeys rule that the 22nd Amendment (or any other inconvenient part of the document) doesn't apply to you because reasons.
