1. He is independently wealthy, and has no public office experience whatsoever. Thus, the normal pressures that cause every other candidate to end their campaign when sufficient controversy arises had no effect on Trump. He had no political career or general reputation to ruin, and he has fuck you money.

2. Unlike Trump, countless other presidential candidates have ended their campaigns in controversy. Thus, there was a mountain of precedence to inform the media that the each week's controversy would be the one that ended his campaign. The result was that every media organization that reported on these events racked up a 13 month streak of being wrong. Its trivial to point this out as a witch hunt after enough time, and at the same time, conflate them with fake news.

3. No matter where you come down on his tactics, its fairly noncontroversial to say that Trump is a master of negotiation. As evidenced by his continually evolving policy prescriptions, he is adept at reading his audience (supporters and detractors), and putting forward messaging that both pleases his supporters, and displeases his detractors. This has multiple positive feedback effects because the pleased take pleasure in witnessing the displeasure of the displeased. The continued pleasure of the pleased is a source of continued displeasure for the displeased as well.

4. Trump makes a lot of obvious generalizations about the world at large: The media sensationalizes, terrorism is problematic, illegal immigration creates a glut of low wage workers, America was a great nation in the past, lobbyists have largely captured congress, the middle class is shrinking, etc. It's trivially simple to control for the variable of Trump, and observe that these phenomena all persist, and have for years. However, there is a psychological element to the consistency of being "right". If you are directly affected by a shrinking middle class, and have to compete with the glut of low wage workers, and see terrorism as a spontaneous event driven completely by religion, and see our government as a corrupt body that breaks everything it touches, you are highly predisposed to attribute unique wisdom to someone who is merely pointing out conventional wisdom. If you already view someone as an expert on subjects of interest to you, you are additionally predisposed to believe in their abilities to fix all of these ailments, without qualification, previous experience, or even the agreement of a single true expert in relevant fields.