Why did Israel target Ali Larijani, and what are the implications if it is confirmed that he was killed?
I see three potential motivations behind the assassination attempt:
One: Israel is trying to literally kill off Trump's off-ramps. Larijani was not only a key figure within the regime who had emerged as the chief consensus builder, but also someone who favored talks with the U.S. and who could build consensus within the system for an Iranian off-ramp at some point.
He also favored de-escalation with the GCC states and supported Pezeshkian's message on that point (though not the apology). There had been some efforts by Larijani to speak directly with senior Trump officials in December, for instance, to prevent the war.
The Israelis want the war to continue to further degrade Iran's military capabilities to shift the balance in the region in Israel's favor for years to come. They have fought for more than two decades to get the U.S. to go to full war with Iran, and having finally achieved that goal, they do not want Trump to cut the war short. Without figures like Larijani in the Iranian system, Trump's pathways to ending the war just got narrower.
Two: The U.S./Israeli strategy may be shifting back to regime decapitation. The reason for this is that it's becoming increasingly clear that reopening the Strait of Hormuz militarily is simply too risky, and there is no international coalition willing to support Trump. But the Strait must be reopened from Trump's perspective because of the impact on energy markets, which eventually will impact gas and food prices in the U.S., and push Trump's own base to turn against this war.
If he cannot open it militarily, then the original idea of regime implosion may prove another path. As such, the killing of Larijani may have been seen as a second bite at the apple. The first bite, the assassination of Supreme Leader Ali Khamenei, did not yield results. But, the thinking would go, a few more assassinations of key figures may do it.
Three: Opportunity. The assassination may have also simply occurred because the opportunity presented itself, rather than having been motivated by either a shift in strategy or a sabotage effort by the Israelis to kill off Trump's off-ramps.
Either way, while this undoubtedly is a significant tactical blow to the Islamic Republic, it is difficult to envision it considerably impacting Tehran's war execution. Plans for these eventualities had already been established during the June war.
Moreover, when relatively moderate voices have been killed by Israel, they have more often than not been replaced by a younger generation of more hawkish voices who opposed Iran's policy of "strategic patience", who opposed the June ceasefire, and who currently oppose any de-escalation or ceasefire.
Whether this was Israel's intent or not, the most likely outcome, nevertheless, is the destruction of potential off-ramps for Trump.
