There is an older article that compiles research from 50 studies, reviews reasons for attrition, and possible avenues to increase retention: https://www.rise.hs.iastate.edu/projects/CBiRC/IJEE-WhyTheyLeave.pdf
It’s interesting to me that on the table about pathways to increasing retention, Purdue has implemented almost every single thing on the list.
Also of note is that of the 50 studies that were analyzed, only 3 found that a competitive environment was a factor in attrition.