The interviews of him i've seen strike me as an STP. I realize the assumptions on this forum are that STs cannot be creative and such, but that is not consistent with the MBTI literature. There is a bizarre manner in which STPs get confused with INFJs when they lead. I think this is because they share all the same functions, but in a different order. INFJs are intensely private. He is a showman, and an incredible business man. He adores shock value - something that INFJs avoid like the plague. He could be the same type as Madonna. These image intense people are strategists in a way that is not compatible with INFJness. INFJs are not image conscious in this way. Few people in pop culture are INFJs - maybe a few method actors and modest, counterculture musicians.
INFJs are very private, nuanced, complex, inward, hidden. Their expression is not overt, shocking, showman style. The reason I am quicker to call DeNiro an INFJ is because he has the capacity to disappear, observe a sea of details and nuance about people, then recreate using intense empathy. I can't swear to either being INFJ, but I'd place a decent sized bet on DeNiro over MM.
I worked for a male INFJ employer. Not even close.
As an INFJ artist myself i can tell you that shock value and drama is not the dialogue of Ni-Fe, etc. INFJ art is intense understatement and nuance.