Not sure where you're getting your info but it appears to be a bit off. And what do you mean by "Clearly #1 of major universities..."?
Per USNWR, under the national universities category (the same as used for their primary overall rankings) Rutgers-Newark has been #1, or tied for it, in undergrad student body diversity since the late 90s, about 20 years running.
> In the most recent ranking based on fall 2017, Newark was once again at #1, in a tie with UNLV.
> Stanford, Houston, and one other tied at #4.
> UCLA tied at #10, with NJIT and five others.
> NYU tied at #25 with three others.
>
Rutgers-NB is tied for #29, with USC, UC-Berkeley, Harvard, and three others.
> UT-Austin tied at #36 with eight others.
> Princeton, Yale, Cornell, and five others tied at #44.
There are lots of ties/groupings due to index scoring methodology, but above is just a sampling of the top 50+ schools comprising the 10 highest diversity index scores according to USNWR. Yes, all of these schools have significant ethnic diversity, but that's not a bad thing. Many of them are highly regarded, nationally prominent schools, including Rutgers-NB. Several have D1 athletics while a few are P5 schools.
Link:
https://www.usnews.com/best-colleges/rankings/national-universities/campus-ethnic-diversity