>No known treatment or vaccine. Targets the decision makers (presidents and ministers and military generals are older, and a virus is easier to reach them, than a bullet is). SARS-CoV has super-spreader events, and asymptomatic spread, making it very difficult to contain. It spreads incredibly easily (near-airborne), in confined spaces such as airplanes, but even the toilet, or shared airco. It offers plausible deniability, by pointing to a natural spill-over event or unsanitary meat markets. It causes enormous economic damage (the economy, not the cannon fodder, being the subject of modern warfare) and cultural damage (tracking is costly and invasive as it damages trust). It is most readily available to small states and terrorist groups by extracting from live civet cats. Military-aged terrorists spreading SARS-CoV by simply boarding airplanes and visiting hot spots, and not even dying themselves, so they can do it all over again. SARS-CoV in first stages has vague symptoms, similar to other, more common viruses, which would give a pandemic a head start. Pandemics are good PR for fear-based terrorism. The strain on the hospitals is enormous, and military-aged men are too worried to reserve a bed for their elderly parents or their recovery.
Not true - there are basically known vaccines to SARS-CoV, they just never got to human efficacy trials because the disease went extinct. But, given their efficacy when repurposed as SARS-CoV-2 vaccines, they were probably quite effective.
As for super-spreading events, this is a double edged sword. It makes it very infectious when nothing is being done to try and stop it, but it means that if there are even cursory measures the chances of the infection stalling are much higher as you're relying on a low number of people actually spreading it.
SARS-CoV may have vague symptoms in the early stages - but it has symptoms. You want a virus that can spread asymptomatically for it to be a major burden, so that makes it less useful.
If your goal is to strain hospitals and create fear, by far the best tools would be humanized avian flu, or a vaccine resistant strain of measles.
>Yes. It would make sense that it would be known. And if it would be known, that would probably sufficiently proof the lab leak hypothesis and end this quarrel. We wouldn't need to talk about probabilities much anymore. But that same argument kinda also works against the zoonotic origin hypothesis. It would make a lot of sense that after a year, we found the intermediate host, or patient 0. If there was a clear epidemiological explanation for a zoonotic origin, it would almost certainly be known. Maybe there really isn't.
I think you're missing the point. If there was a lab escape, the likelihood for the sample to be known is very high. This means that given priors of no known samples, the likelihood for a lab escape is lower.
It's also completely unrealistic to expect to find the host or patient zero after a year for a zoonosis. It took 40 years to find the intermediate host for Ebola, and four years to find it for SARS. For some epidemics, we never found a solid intermediate host. Patient zeros are basically never found, either, unless the disease is incredibly pathogenic and virulent - which SARS-CoV-2 isn't. If you look towards past epidemics that originated from zoonosis with a similar disease profile, you will find that it takes years to decades to conclusively find an intermediate host, and that patient zero is basically never found with any degree of certainty, meaning that the current scenario is perfectly congruent with expectations.