https://en.m.wikipedia.org/wiki/Rise_and_Kill_First at least one group of people appear to have accepted at least some of your argument.
Furthermore, assassinations fall into three categories:
Where the assassin takes credit afterwards (for intimidation, bragging to supporters, etc), where a third party is blamed (to prevent reprisals being directed at the source), and where it is unclear that an assassination was performed (wow IBM got screwed hard by that plane crash).
From the perspective in the OP, it is clear that there is a detection challenge. The most useful categories (to an assassin) are the third and the second, the least useful is the first. An external observer will see only the first category, and a potential subset of the second category, but is unlikely to see many members of the third category.
Maybe they're very common, and you're just not seeing the obvious.
Even the Israelis, though, will concede that assassinations are tactic, not a strategy. The fact that they call their assassination campaign "mowing the grass" indicates the level of confidence they have in assassinations as a means of bringing a decisive end to a conflict. At best, assassinations buy time until the conflict can be ended through other means.
I agree, but shouldn't the unattributed assassinations be somewhat detectable? I think it's somewhat hard to mask a sabotage as an accident. (I guess I am trying to say that there should be a big class of assassinations that there is nobody to blame for.)
The intersection of people with the skills to succeed at (and get away with) such a murder, the skills to predict whether it will lead to their preferred financial or political outcome, and the psycopathy to think that it's worth it, is vanishingly rare.
All of these things are easy to underestimate:
Off the top of my head:
People willing to commit murder are typically those with little to lose. In order to make a significant amount of money from shorting, you have to have a significant amount of money already. Yes, rich people often want more money, but they’re unlikely to tolerate the high risk of committing a murder when there are many less risky ways of making money.
If the USA assassinates foreigners, foreigners can fight back. It’s in everyone’s best interest to maintain a low-assassination equilibrium instead of a high-assassination one.
Some of this is done in war. Why not outside of war? See 2.
If the USA assassinates foreigners, foreigners can fight back. It’s in everyone’s best interest to maintain a low-assassination equilibrium instead of a high-assassination one.
This is the standard, game-theoretic reason I've always heard. Assassination and sabotage are effective and can be carried out with enough secrecy that no one could necessarily prove you did it, but engaging in them creates a world where you have to defend against them because they are normalized, so it's a tool that gets reserved for only those cases where it is deemed to be worth the risk.
Political goals seem ripe for assassination
That is a huge misconception. Can you name a single US assassination of a foreign head-of-state, in the last 50 years, that didn't blow back on us? In every case I can think of, where the US has assassinated a head-of-state, the state has either ended up collapsing into instability or has eventually replaced the leader with a leader that was even more hostile to the United States.
Also, depending on your model of history, assassinations may be completely ineffective. If historical events are the result of large historical trends converging, then assassinating any particular politician might shift things around by a few years, but may not actually stop events from occurring.
Political goals also seem ripe for sabotage.
Also incorrect. This was tried in the 1970s by a number of far-left revolutionary terror groups, both in the United States and Europe. Weatherman, Symbionese Liberation Army, Red Army Faction, the Italian Red Brigades, all tried overthrow their respective states via a campaign of terror bombing and sabotage. They all failed. The book Days of Rage, by Burrough, chronicles many of the American revolutionary groups, and how they were all eventually either hunted down or scattered by state pressure. (If you don't have time to read the book, David Hines has an excellent summary on the blog Status 451).
As it turns out, nation-states are pretty resilient, and can remain functioning even in the face of enormous pressure, and a guerilla campaign of sabotage and assassinations hardly constitutes any pressure at all, much less enormous pressure.
Even psychopaths are risk-averse. Why take on the physical risk of performing assassination or sabotage when you can take on a much lower risk (for similar reward) via white-collar crime.
I sense it is mostly because people naturally refrain from murder unless it is seen as a last resort measure, or has hugely positive consequences.
A certain fraction of population is psychopaths. On global scale there are literally millions of them. They can get the starting capital e.g. by theft. Why don't they use this strategy?
Because if you have the kind of intelligence and common sense to clearly see and care about the wrongdoings of politicians, this same intelligence would suggest the idea, that ending the life of one or several of the endless supply political miscreants, would be fruitless. The reward would not balance out the risk. Killing a person is possible but killing stupidity and/or evil is impossible because it is a scale.
The only hope seems to be to continue to permit these self-centered, ego-inflated, ignorant (or often intentionally evil) politicians to publicly broadcast their stupidity, and cruelty so all people can easily see their true colors and promptly dismiss anything they say or do as incoherent babble and self-aggrandizing actions.
While i dont have a definitive answer, i will say one of the reasons that left wing political movements nowadays (Occupy wall st, BLM, the environmental movement) dont have the same pronounced leaders that the left wing movements of the 1960's did, is due to the targeted arrest, harassment and assassination of those leaders by authorties.
Was that actually the plan or just a post facto explanation? My prior would be that this happened because of the organizing mechanisms of the day (internet vs in-person meeting of the past).