The strategic danger to Israel posed by the Shia may sound “logical” on the surface.
But the Israeli support for the radical Sunni forces is very shortsighted and will have grave repercussions in the long run. Leaving aside the fact that it is highly immoral and reprehensible.
On the one hand the Sunni’s (Turks and Arabs) may be not the smartest guys around... but they are cunning, shameless and have much more influence in Western countries than the Shias (who have Russia and to some extent China on their side). Iran, Assad and Co. are quite isolated in the West, while the Saudis have bought a lot of influence in the US and Europe. The Muslim population in the West is mostly Sunni and politically directed by Turkey and Saudi-Arabia. Of course also the global Jihadi terrorist threat is Sunni and lead by Saudis.
The Shia may be a regional rival for Israel, but the Sunni “Ummah” (over 90% of Muslims) is a global menace of largest proportions.
It would be smarter to let the Shia in the region curtail and destroy Sunni Islamism. Israel is still a great power militarily and has the US firmly on it’s side. If attacked directly by the Shia coalition, they can defend themselves. As long as the Shias are destroying the Sunni jihadis, let them do it and stop interfering.
It is not acceptable that the Sunni jihadis exterminate all non-Sunnis (Christians, Shias, Druze, Yazidis, moderate Sunnis etc.) and establish terrorist bases across the Middle East. That’s the worst case scenario and inevitable result if the Shia alliance is prevented from destroying the Sunni jihadis.
"A Clean Break" won't end well. https://en.m.wikipedia.org/wiki/A_Clean_Break:_A_New_Strategy_for_Securing_the_Realm