You don't get tenure for being a good teacher or for being supportive of your students. You get tenure for doing impactful research, and lots of it. The post focuses almost entirely on non-research contributions, citing only a $175,000 grant and an acceptance to ACM CHI conference as the prof's research bona fides. Of course, this is likely written from undergrad's perspective, but take a look at Lerner's Google Scholar profile:
https://scholar.google.com/citations?user=BkZor8wAAAAJ&hl=en.... Tbh I don't know how strong Wellesley CS is, or how the other profs there compare, but that's just not an impressive research record for someone four years into a tenure-track position.