Actually, Lin Manuel Miranda said right out that he wanted a cast that “Looks like America is now” and issued a casting call for “no whites”.
It does not get any clearer, fam. If you don’t cop on by now, you never will.
Apparently he missed the latest census data that says the United States is still 60-70% caucasian. If his cast "looked like America is now", 7 out of 10 cast members would be white. Sounds like he decided to cast the show more along the lines of how the Dominican Republic is now.