Iran is not strictly "an obstacle" to Israeli hegemony. Its ideology since the 1970s clearly states the destruction of Israel as its goal. It clashed with Israel over Iran's desire to set up a Shia vassal state in Lebanon and it killed Jews and Israelis all over the world through terror (e.g. AMIA bombing in Argentina)

The Palestinians are merely a tool for Iran to gain influence, Hezbollah and Shias in Iraq were far more important for them historically