The world will still have a good deal of oil, but prices will rise. That would be inconvenient, but survivable. Closing the Strait of Hormuz would not only shut off Iran's seaborne access, it would shut off Iraq's and Saudi Arabia's exports, along with Qatar's and the UAE's. I rather doubt that would leave the world with "a good deal of oil". It would be enough of a shortage to cause severe dislocation.
Saudi has been at the oil business too long not to have noticed geographic problems. They also have a huge network of pipelines that take their oil whereever they want.
When an economy is dependent on one commodity, as Iran's is, that becomes it's tipping point militarily.
Military reasoning is one reason that Iran wants to develop alternative sources of energy...namely nuclear. So, their insistence that they want nuclear energy is true.
They also want the bomb, but that is because they have hatreds and expansionist dreams.