Israel and US supported the Shah of iran which tortured many of the people which are now in power.
Israel is seen as America's thorn in the middle east. Iran wants to take its place as a regional power and must oust american presence, be it in iraq or israel.
For years, the Sunni nations have tried to defeat Israel, Iran wants to take the credit of success, thereby proving the Shia are better than the Sunni.
Irans strategy, therefore, is to prompt up proxies and gain influence via force of arms (militias in Iraq, civil war in Yemen, Civil war in Syria, lebanon) in the hope that all of these could pressure Israel enough until it cracks.