this is what i've found on his wiki.

Eurovision controversy and disqualification
Klein performed in the 2024 Eurovision Song Contest's second Semi-final and was scheduled to enter the Grand Final with the entry "Europapa". However, it was announced that Klein had stopped all further rehearsals until further notice due to an incident. On 11 May 2024, the day of the final, it was announced that Klein had been disqualified from the Eurovision over alleged verbal threats to a female production worker.[18]

The night before the Grand Final, Klein was spotted in a hotel, appearing distressed and ignoring paparazzi. This may be attributed to a moment in the 2nd-Semi Final press conference the same day, where Joost said "Why not?" after a staff said the Israeli entry was not compelled to answer the controversial question if she (Israeli singer) thought that she (Israeli singer) being there endangeres others (Due to terror threats againt her).[19]