Their ambitions were no worse the our's.
Please do not misunderstand me, DURING the war the Japanese did many many horrible things to captured people. Their conduct during the War was awful. Nothing excuses this, but the reasons that the war started in the first place has little to do with their conduct during the war, or their surprise attacks.
Maybe I'm misremembering here, but I'm pretty sure the Nanjing Massacre was a good bit before poor lil' set upon Japan was "forced" into attacking every other power in the region.
And it wasn't just captured enemies. Thailand was a Japanese
ally and yet tens of thousands of Thais were worked to death along with Allied POWs and civilians from subjugated countries. The Japanese had been treating Koreans the same way for decades. Their empire was savage and brutal even compared to the worst excesses of European colonialists.
The Japanese government of the day was no better than the Nazis, and in many ways worse. They were hyperviolent, routinely assassinating anyone who dissented from their lust for conquest. One reason Yamamoto was given command of the Combined Fleet was to give him a seagoing command and get him out of Tokyo because the Navy leadership understood that if he stayed in the capital he was certain to be assassinated for opposing the Army's warmongering (on pragmatic, not ethical, grounds). Think about it, this was the guy who was chiefly responsible for the attack on Pearl Harbor, and his own government was going to murder him for being too pacifist! And this cult of aggressive war and rule by assassination went well back into the preceding decades, long before the US or anyone else imposed sanctions on Japan. The government was hanging Buddhist priests in 1911 for opposing the government's militarism (among other things) - Google Uchiyama Gudō sometime.
The Roosevelt administration was generally anti-colonial and the US had already committed to freeing the Philippines, its only significant colony in the Pacific. The reasons it rightly resisted Japanese aggression were, in no particular order, (1) Desire to prevent a Pacific distraction from the all-important task of defeating Hitlerism in Europe, (2) The many, many routine and well-documented atrocities carried out by the Japanese in China without the slightest shred of justification, and (3) Desire not to see a European hegemony in Asia that was plainly (to anyone but the colonial powers) on its eventual way out replaced by Japanese hegemony that was orders of magnitude more brutal and potentially much longer-lasting. I don't see how anyone could take issue with any of these motives.
The Allies in Asia and the PTO were not always in the right, but that doesn't mean that Japan was not always in the wrong. The Russian government was pretty nasty too, but that didn't excuse Hitler for unilaterally launching a war of pure aggression and extermination against the people unfortunate enough to live in the USSR. Japanese people weren't inherently bad any more than German people were, but their government in 1941 was absolutely atrocious and didn't need arm-twisting from anyone to launch aggressive wars against anyone who had stood in the way of anything they wanted.
Of course, this doesn't have much to do with the lack of interest in Japanese warplanes. For most aviation buffs planes aren't political. But I wouldn't confuse lack of interest in early war deathtraps with lack of interest in Japanese planes generally. I love flying (in-game) and reading about WW2 Japanese planes, and planes like the Ki-67, Ki-84, and N1K2 are valuable additions to the plane set, but the Ki-43 would be nothing but a target in the MA, it has absolutely no virtues to recommend it. It's a bamboo and rice paper tinderbox whose pathetic armament alone would make it nothing but cannon fodder against anything other than Zekes or other Oscars. Just look at the G4M - how often do you see those anywhere except perk farming in deserted arenas? Why on earth would anyone fly one in the MA except as a joke?
There's also the romance factor. Most other nations made a cult of their own aces and as a result people tend to know a lot more about them. For their own political/psychological reasons, the Japanese government didn't do this; it much preferred making a cult of servicemen who died. People want to fly the planes flown by the great aces they've read so much about, less so the planes mostly famous (at least after the first year of the war) mostly for being shot down in record numbers.
