The idea that Trump would be tasked with being the front man of Operation: Take Back America if he had a criminal past, or that he would commit crimes and risk everything is ridiculous. As if the future of the country, and literally the world, would be placed on someone whose actions could end the entire mission. Those who approached Trump to do this are not stupid. He is clean.
"If a builder [in NYC] wants his workers to show up on time, he has to be involved with mobbed-up unions." -American Mafia Documentary
That does not mean all builders in New York are criminals. It means they are forced to deal with them. They are not then considered crooked.