So we take a pragmatic approach based on our best information at the time, and as quickly as possible. How do you stop a dictator with the world's largest arsenal of nukes from engaging in a 19th century style land grab without destroying the world political order, world economies, and perhaps even the world itself? Now how do you do it without creating a power vacuum?
It's easy to stand back observing the results and criticize in hindsight (and believe me, we'll get plenty of that in a few months), but right now people need to make quick and possibly inefficient decisions using whatever information they can gather because the consequences are so grave.
But such argumentation is fruitless.
In practice, sanctions rarely if ever seem to cause violent revolution. They just end up hurting the little guys who can't do anything anyway, whilst the most well connected work around them anyway. See how North Korea has Apple computers ... for the leadership.
Sanctions aren't supposed to cause violent revolution, particularly.
They are supposed to:
(1) Pressure the regime to change the course of action which caused them, and
(2) Reduce the economic capacity behind, and this the effectiveness of, the targeted action so long as #1 doesn't work.
Promoting violent overthrow of the regime is a manner of achieving #1, but while it is often an acceptable outcome from sanctions, it's generally not the preferred outcome.
> They just end up hurting the little guys who can't do anything anyway
All, even the most autocratic, regimes rely entirely on the at least tacit cooperation of “the little guy” to function at all.