Rome's Caesar was successful in conquering Rome. Why was Mongol's Kubilai Khan unsuccessful in conquering Japan? Both situations were pretty much similar.
Actually the two situations are not similar.
1. Rome was big on imperialism. The Mongols were still basically at heart raiders and often ignored concrete political power in an area in favour of advancing further and making the locals do the work.
2. Japan is further away IIRC. The oceans might be a bit meaner there too.
3. Opposition: The Japanese were better organised and equipped to repel the invasions than the assorted British tribes. Especially since the Japanese had a taste of Mongol tactics with the first raid and could adapt.
4. IIRC the Romans were able to recruit locals to help out their effort, the Mongols couldn't or didn't.
It's like natural disasters had to do something with men's will to military conquest. Is it really possible?
The effect was multiplied by the Mongol practice of retreating to their ships (again, a result of the raider mentality). Hence bad weather didn't just destroy transport, it destroyed the Mongols as a raiding force.
It's like Columbus could not have discovered America if there were strong hurricanes in the Caribbeans.
Well if the storms sank his boat then, yeah.
It's very unbelievable that the mighty Mongol invading forces could not conquer Japan because of typhoons.
They couldn't conquer Western Europe because 'some guy' died. Sure he was Ghengis Khan... but then, sure, we are talking about a typhoon here.
If they failed at first really because of typhoons, why couldn't they come the next year or the next? The distance between the invasion base of Koryo dynasty of Korea and Japan is somewhat similar to the distance between England and France. They couldn't land on Japan because of some storms?
Maybe it was viewed as too hard a task with little benefit. Further, who was supposed to give the order to invade? The Mongols at the best of times were not all that centralised, it was physically difficult.
But, still, no historical records and books have been found or written that conclude that Mongols had conquered Japan and included it as their territory. It's just very easy to question this historical conclusion.
How about the absense of Mongols in Japan today? Or Japanese artisans or what have you being shipped to Korea etc.?
Both Napoleon and Hitler got kicked out from Moscow with the help from the cold.
Here in lays a problem with your thinking. Napoleon and Hitler, like the Mongols, were not just defeated by weather. In fact, the opposing military force had a lot to do with their defeat or retreat. Japanese forces beat the Mongols in battle, they retreated, their boats were wiped out.
But again, as I said, typhoons do not last long time. If, the Mongol ships were all destroyed by the typhoons, then perhaps, they could not make more ships back home and start invasion again. That probably is the only convincing reasoning behind why Mongols failed to conquere Japan.
How do you know the Mongols even knew their fleet was destroyed? If everybody in the force died, the Mongol command might have assumed the Japanese annihilated it and hence were too hard a nut to crack (one possibility).