That is fundamentally untrue. In Venezuela, regime ended up completely intact, except the change on the top. There is no "clearing the path" and there is no "regime change".
In Iran, protests stopped. The lead was replaced by more hardline lead. Nationalists now wont go against the regime, even if they dislike it.
If they loose control over country, there will be civil war and unrest, but all chances of some moderates consolidating power went down. Or, even more likely, regime wont fail and will have stronger grip over the country.
> Russia loses its drone and missile manufacturer,
This war is massive gift to Russia. The sanctions are removed, the oil prices go up. Russia wants this war to go on as long as possible, it is like a lifeline for them.