Israel would have anticipated Iran had to respond to its embassy being bombed. I imagine Netanyahu felt the opportunity presented by having 7 key enemy military officials in the same place at the same time was too good to waste. He also would have judged that Iran's inevitable violent response (whatever it may be) would garner more support from the west, given it's been flagging.
What we don't know yet is what Netanyahu's next move will be. I wonder if he'll take our Iran's growing nuclear capability. Frankly, that'd be a benefit for everyone and take us all further away from WWIII than where we are at present.
As a side note, Israel's multi-layered air defence system seems remarkable. It amazes me that no one has commented on why it's necessary to exist in the first place and how frightening it must be to live in a place where it might be needed. I'm grateful not to be surrounded by enemies at every border and have to have air raid shelters in my home / nearby that I have to rely on to keep my friends and family safe.