The Hungarian uprising was killing Jews in the street. It was anti-Semitic from the beginning and the “Jewish Bolshevik” idea from the Nazi era was a motivating factor with the fact several leaders of the Hungarian government were Jewish cited as a battle cry.

https://www.jta.org/2006/10/25/lifestyle/1956-crises-decimated-two-communities

After the uprising, 200,000 Hungarian Jews fled the country fearing it signaled a return of the antisemitism of the recent Nazi-collaborationist regime of the 1940s.

Sending the tanks in to stop this was a good thing. It would have been better if the anti-Semitic uprising was stopped before the pogroms started.