I'm not talking about the ability, I'm talking about the will to spill your soldiers blood for such a purpose. A boots-on-the-ground invasion is off the table because western countries would consider that price far, far too high for such a goal. I mean, muster a large scale invasion, for what? A couple dead journalists? Looking at other potential interventions, even literal mass concentration camps would probably be tolerated without escalating to an invasion. No, the western political will in this case is definitely limited to sanctions only. They might perhaps assist one side in a local conflict (i.e. the locals provide "boots on the grounds" and any blood to be spilled, while outsiders provide money and arms), this has happened in quite some places, but in Belarus there isn't an ongoing violent conflict between two sides, there's just the state applying small scale police action against individuals, there aren't any "rebel organizations" that would be capable of receiving such support.

> Belarus triggering a defence treaty with Russia?

We'd expect Russia to come in with force to prevent a pro-western government forming, treaty or not - e.g. if it seemed that Lukashenka would agree to cede power to a pro-western opposition, I wouldn't be surprised at an intervention from Russia even if Lukashenka would object. Once again, such scenarios were discussed and considered credible last year, but weren't "tested" as it turned out differently.

> Russia will not come when faced with credible force.

Perhaps, but there isn't a credible will to apply force, so any threats of such force would be treated by Russia as obvious bluffs.

> Any government in the world can be overthrown by a popular revolt. Any.

Of course, but a popular revolt isn't happening in Belarus, the opposition chose (and are still choosing) not to revolt and limit their activities to nonviolent protest - if you'd call that defeatist, I might agree, but that was the initial position and they seem to have succeeded in spreading that doctrine, and it would take time to reverse it. And the lack of practical reaction of people to the state abuse of power and the failure of various attempts at general strikes indicates that the conditions aren't even close to a revolt.