In national politics, one calls for the vote when the outcome has been decided, in order to "put a bow" on matters.

Trump can be expected to pull a trigger when the results are similarly "known" (Maduro), and not a moment before.

The Iranian situation is orders of magnitude more complex than Venezuela, and the stakes are obviously higher on both ends. If the Iranian autocrats persevere, they will argue heaven is on their side. If Trump fumbles, the Loyal Opposition will be a proxy for the Ayatollah at the midterm elections this November.

For one who (according to his detractors) is an idiot with no self-control, Trump shows much strategic patience.