She was never into Black culture. She wasn't even that relevant for Black folks in general.
If there was a celeb they should like it should be Lena Horne or Josephine Baker. But why Monroe?

ya'll be trying to hard
some people reach iconic status....even is she was a whore, crazy, lacked talent, or whatever....the public still adored her just like the countless other sirens before and after her....she had "it" factor...it's simple really
and last i checked Lena Horne and Josephine Baker are included on the same level of icon status...
also...doing a quick google search helps before posting broad statements...MM was into equality for american minorities and other non white/non american groups....and Ella Fitzgerald was greatful to MM for one noteworthy act...they later become prett good friends because of it
“I owe Marilyn Monroe a real debt…it was because of her that I played the Mocambo, a very popular nightclub in the ’50s. She personally called the owner of the Mocambo, and told him she wanted me booked immediately, and if he would do it, she would take a front table every night. She told him – and it was true, due to Marilyn’s superstar status – that the press would go wild,” said Fitzgerald. “The owner said yes, and Marilyn was there, front table, every night. The press went overboard. After that, I never had to play a small jazz club again. She was an unusual woman – a little ahead of her times. And she didn’t know it.”