What kind of tin foil hat is this? Isn't it simply more likely that any number of announced opponents, Republican, Democratic or independent would dig up dirt (real or otherwise)?
His national reputation was mostly based on The Apprentice and his PR efforts. It's not a surprise that people changed their opinion of him when he announced he was running, because in his announcement he accused Mexico of actively sending criminals to the US, and his solution was a humanitarian, ecological, and financial disaster of a wall. This of course would not even address the majority of policy violations in immigration (over staying visas). His ridiculous promise that Mexico would pay for it was also an obvious farce. It was a wake up call to people who had previously not scrutinized him very much, particularly in a political context.
What's "weird" is that anyone took him seriously after that.