Hitler had a united party, a divided opposition including a party who didn't care what happened as long as the interests of a particular institution were protected, an actual Communist party to blame, and a pliant, senile boss with enormous reserve powers. Sure, the possibility of a machtergreifung are non-zero, but then again they're non-zero in any country. Even the most locked-down USA would be more open than 1970s USSR or China today, much less 1930s Germany.