The key reason to support Hitler and the Nazi regime was Hitler himself. Aided greatly by propaganda genius Goebbels,
Hitler was able to present an image of himself as a superhuman, even god-like figure. He wasn’t portrayed as a politician, as Germany had had enough of them. Instead, he was seen as above politics. He was all things to a lot of people – although a set of minorities soon found that Hitler, beyond not caring about their support, wanted to persecute, even exterminate them instead – and by changing his message to suit different audiences, but stressing himself as the leader at the top, he began to bind the support of disparate groups together, building enough to rule, modify, and then doom Germany. Hitler wasn’t seen as a
socialist, a monarchist, a Democrat, like many rivals. Instead,
he was portrayed and accepted as being Germany itself, the one man who’d cut across the many sources of anger and discontent in Germany and cure them all.
He wasn’t widely seen as a power-hungry racist, but someone putting Germany and ‘Germans’ first. Indeed, Hitler managed to look like someone who would unite Germany rather than push it to extremes: he was praised for stopping a left-wing revolution by crushing the socialists and communists (first in street fights and elections, then by putting them in camps), and praised again after the Night of the Long Knives for stopping his own right (and still some left) wingers from starting their own revolution. Hitler was the unifier, the one who halted chaos and brought everyone together.
