On December 5, the Israeli public channel "Kan 11" revealed a Russian request to Israel not to interfere with Russia's actions in transferring Russian defense systems from Syrian territory to the battlefields in Ukraine.
According to the channel, in recent days talks were held between senior Russian and Israeli senior officials in this regard, and indicated that Russian officials hinted to the Israelis that Russia's loss in the Ukraine war would inflame the feelings of hostility towards the Jews in Russia, and that Putin is the one preventing this.
One of the aims of the Jewish state is to safeguard the wellbeing of Jews in the world. If this report, by on of the top Israeli news channels is true, you may have the reason behind Israeli policy of no arming Ukraine.