One argument for why militarists became so powerful in Japan in this period is that the Japanese public had lost faith in government institutions. There was basically an inter-class struggle in Japanese society at this time between the higher, wealthier classes and the lower, poorer classes. Members and participants of militaristic groups at this time felt that military rule and totalitarianism would be better for the lower classes than capitalism. This general resentment among the Japanese public and particularly among the young military officers resulted in growing support for militarists.
I don't know if these developments made World War II inevitable, but it is certain that they caused Japan to align with Germany and Italy in WWII. And since the Allied powers (Soviet Union, Britain, US) won World War II, this led to the consequent attacks on Japan in 1945. So we can say that militarism cost Japan much death and destruction.