As evidence I point to Boys Town, a philanthropy that quite literally exists to take care of orphans. It amassed a large fortune that exceeded anything justifiable by their core mission. In the 1970s, a tip from Warren Buffett on this won The Omaha Sun (which he owned at the time) a Pulitzer for reporting on the resulting scandal. (He was also an investor in The Washington Post which won a Pulitzer in the same year for reporting on Watergate.)
See https://www.philanthropydaily.com/nonprofits-mission-drift-b... for verification. And evidence suggesting that that particular charity has continued down the same path.