You're mistaking lack of overt hostility with friendship. By the same logic I could say the US and China are friendly nations to one another, just because they're not actively fighting a war. But that won't make it true. The entire cold war was characterized by a de facto war being prosecuted without going "hot", instead through proxies.
During the cold war, the USSR was a major antagonist for Israel. It supported, armed, and even fought beside - the Arab states that waged war on Israel.
When the USSR fell, Russia remained an arms supplier to Israel's enemies. Syria, Hezbollah, Hamas, Iran, etc - all had modern Russian, not Soviet, weapons.