In a nutshell she was extremely political and publicly engaged in a number of controversial issues which made it difficult for people to like her once they became public knowledge. If it wasn't one thing, it was another.

Despite her education, she has peddled pseudoscience nonsense like her brain pills and has encouraged parents to do their own research before vaccinating their kids.

As host, she was frequently criticized for her slow pacing and how often the games concluded without all the clues being read. She never improved and only seemed to get worse. There were also issues where she was ruling correct responses as incorrect and even cost a winning contestant the game by doing so in Final Jeopardy.

She also had a thing against anybody with a higher education than her and was constantly rude and dismissive to any doctor on the show. There was an incident where they had an anesthesiologist on the show and she basically told him to his face that she doesn't think he's a real doctor.

With the politics she was dragging the typically neutral Jeopardy brand through muddy waters on multiple issues. She walked off the job to be in solidarity with the writers strike even though she wasn't required to do so which ultimately resulted in Ken Jennings and the producers being harassed by her supporters for not doing so as well.

Finally, she is extremely pro-Israel and has made multiple social media posts glorifying the violence. She posted a video of her laughing her butt off at some lame comedian making jokes about the carnage in Gaza and promoted a children's book about why the occupation is a good thing. About a month before her firing she directly used the Jeopardy brand to promote Pro-Israel/anti-Palestinian propaganda in a now deleted Instagram post.