Again, review the methodology for each ranking.
Examples:
https://www.topuniversities.com/qs-world-university-rankings/methodology
http://cwur.org/methodology/world-university-rankings.php
http://www.shanghairanking.com/ARWU-Methodology-2017.html
https://www.usnews.com/education/best-global-universities/articles/methodology
https://www.usnews.com/education/best-colleges/articles/how-us-news-calculated-the-rankings