2pac had out one album and had been in two movies at that pint he was nowhere near an Icon.
Also while Pac have talent he was never even in his best role on the level of an actor like Denzel.
Maybe not iconic status as we know him today but then he was still a big deal. Pac was at the beginning of his fame and was being highly sought after. He had just released his second album and was in poetic justice the same time Menace was out.
I didn't say he was on the level of Denzel in acting talent I was speaking in terms of status. 2pac has a fanbase, he was a bigger draw than any of the other actors in that film. He was a popular music artist. Hughes bro's knew that. The falling out is a common conflict with actors vs directors.