The necessary dose of reality
I would be doing you a disservice if I pretended this was a sure thing. Investing is never a guaranteed win. Banking on Middle Eastern geopolitics is a notoriously brittle strategy.
This US-Iran agreement is an interim deal. It is a temporary plaster, not a permanent cure. The diplomatic history between these two nations is essentially decades of hostility, punctuated by very brief moments of awkward cooperation. If negotiations collapse, or if a domestic political shift ruins the mood, the oil price will spike before you can even log into your brokerage account. This is a tactical trade, not a lifelong marriage to transport stocks.
Then we have the broader macroeconomic gloom. Central banks have been keeping interest rates painfully steady. If global growth grinds to a halt, people will simply stop booking flights and cruises. A cheap fuel bill means absolutely nothing if your planes and ships are empty.
Finally, the financial benefits will take time to show up in quarterly earnings reports. You might need to wait months to see the actual numbers validate the theory. All investments carry risk. Putting your capital on the line means accepting that you might lose money.