Err... did I misunderstood the question, or do (nearly?) all commenters have no idea what they're talking about?
You're asking why Israel doesn't assassinate Hamas's top leaders, right? Or did I misunderstood and you asking Israel doesn't ONLY assassinate Hamas's top leaders? Or are you asking why Israel responded differently to Munich?
To answer the first question, well... they are. Hamas's top leaders according to BBC are:
- Ismail Haniyeh - Killed.
- Mohammed Deif - Probably killed.
- Marwan Issa - Killed.
- Mahmoud Zahar - Alive. is 79 years old and might not be active/influential in the leadership.
- Khaled Meshaal - Alive.
- Yahya Sinwar - Alive.
Also, keep in mind that the response to the Munich massacre took about 2 decades.
As to why Israel dosen't ONLY assassinate Hamas's leadership, the simple answer is that it won't solve anything. It won't bring the hostages home (It will probably have opposite effect as a. it will leave Israel without a centralized entity with whom to negotiate and b. Sinwar might be using hostages as human shields, which also might explain why he's still alive), and it will still leave Israel with a terrorist entity next door. The official Israeli version is that the assassinations, among other things, serve as leverage on Hamas leaders to secure a deal. Obviously, this is only effective if there is some leadership left.
If you're asking why Israel responded differently to Munich, it's because the situation is totally different in numerous ways. But the question itself is also factually wrong - Israel didn't only assassinate the leaders of Black September. Firstly, the goal was to "assassinate individuals they accused of being involved in the 1972 Munich massacre", not just the leaders. Not only that, Israel also responded with raids and bombings (for example: 1973 Israeli raid in Lebanon).
I think trauma and hardship in general isn't additive, rather multiplicative or exponential.
Like, once there's a "core" trauma, small every day issues seems bigger and harder to deal with, and that kinda builds on itself so any new hardship seems bigger and bigger and so on.