For the first question: You make a star. You don't need to get a top actor at this point because the brand sells itself and you turn someone into a star.
For your second question, context matters.
There's a reason Danny Rand was creating as a white guy during that period and it had everything to do with them being about creating a main character who wasn't a white male while at the same time wanting to hop on the Bruce Lee train. So they made Danny their version of Kung Fu, the white guy who's taught by asians and masters martial arts better than them, because that's what the politics and societal norms at the time told them they had to do. It's possible to do something different now and get away from the admittedly touchy racial issues of the mid 70s. There's a reason Neal Adams created Jon Stewart and it wasn't just because he thought it'd be fun. He wanted to make a statement.
That said, I'm not against what they did with making Danny a white guy. But I understand those who feel like it wasn't the right move