well, you can view it Iranian are willing to insure the vessel for $2M fee - that it will not get hit by them during the crossing ;). Once they are in the Oman sea, they can use traditional insurance.

You can view it like that, but most people don't. At least the people involved manning those tankers don't.

And why should them? It appears that the Iranian armed forces started acted quite autonomously, by design. They know that communications are not secure, so local commanders have a very high latitude in what actions they deem correct to take. If such a commander deems that asking and collecting $2 MM per vessel is a good idea, they'll do it. But if another commander thinks that sinking a passing vessel is what their standing orders are, they'll do it too, not being aware that the toll was paid. So, if you are the captain of such a vessel, what do you do? Do you complain to Iran for not holding their end of the bargain?