British Ambassador to Japan Julia Longbottom explained that her decision was because the city did not invite Israel to attend. Longbottom told reporters that unlike Russia, which invaded Ukraine, and Belarus, which cooperated in the invasion, Israel is exercising its right to self-defense. So, treating Israel in the same manner would be misleading, she said

U.S. Ambassador to Japan Rahm Emanuel will also skip the Nagasaki peace ceremony. According to the U.S. Embassy, Emanuel does not want to politicize the Nagasaki event.

the envoys of Group of Seven nations, except for Japan, and the European Union said that if Israel was excluded from the invited countries, it would be difficult to send high-ranking officials to attend the ceremony.

Totally not politicized. I guess supporting Israel is a better look than opposing nuclear warfare.