He never explicitly said he would be a one term president or necessarily saw himself as one. I looked back to double check again, and he only made cagey statements about seeing himself as the transition between generations. A two term president could still qualify for that. The more explicit one term stuff was from his aides saying he was considering that

Should he have just been more direct, yes, but what he said was nothing as explicit as directly stating we need marijuana it to be legalized