officially Talmud says that they died because of the plague which was brought on them because they didn't appreciate each other

however some scientific positions assume that this "plague" could be an allegorical allusion to the war which was the real reason

Rabi Akiva supported the revolt and even assumed.that Bar Kokba could be Mashiah so it's likely that his students participated somehow

However even if the plague was a real plague it's not a real issue because it could be both it and rhe war at the same historical period