You should not focus on germans.
First of all 1990 is not 1914 or 1939 (or 1933 if that matters) and secondly any other nation could have started any of the two wars. Strictly speaking WWII started in asia anyway and germany only opened the fighting in europe.
At that time, and we still have similar attitudes, but people try to accomplish that with other means, people believed the stronger can simply take from the weaker. That is called fascism.
At WW I the excuses where insults to the various majesties that could not be left 'unpunished'. The king of england, ir was it Victoria? ( to lazy to look up) was actually a cousine if the german emporer. Nevertheless they went to war.
I saw an documentary like 19 years ago, there was an like 90 years old german lady interviewed about her perception of WW I.
She said like: """
When the war was about to start, everybody told us it will be over in three weeks. (Likely because of the remembering if the french/german war around 1870)
They told us neither the frensh nor the britts can fight.
They are no match for a proper german soldier who loves his emporer.
They told us the britts will come, and after 3 days they miss their cricket, their polo and their other sports and want to go home.
The french would not even fight, because they are so obsessed with fashion. And most are gay anyway.
"""
So the interviewer asked: "And you believed that?"
The lady: "Of course! when you saw a soldier it was a dashing german or an austrian one! If you saw a britt it was in a (sports) magazine, a guy in tweet with an umbrella looking important. If you saw a frensh it was an feminin looking guy in a fashin magazin, with a scalf in a strange colour. No one believed they would put up a fight and 'dig in' in the western frontier"
Wording partly by me, except for the sports the fadhion and the gayness.
People at that time (and actually still today) did what they thought they can get away with. Russian / Turkish war, war against the turks in north africa/levante/arabia. Expanding to the east drawing germany etc. into war. Genocide against the armenians, spy phobia with lynch mobs against any 'foreiners' all over west europe. Slight shifting without any distinguished interruption via itallian fascism to spanish fascism to german fascism to WW II.
There is no difference in Japan. Or if China had been industrialzed earlier instead of being kept down by britts, americans an dutch, they had attacked the rest of asia.
All that Euthanasie crap, was invented in the USA. Well established law there. Abolished decades after WW II. After the americans realizes to what ends it had lead in germany.
Resources, Lebensraum? That was a lame excuse for having a mindset from the late middle ages but having the tools of a modern world.
And it is happening again. Right here. Right now. With Gene food, patent laws, trade agreements farmers in third world countries get driven into suicide or bankruptcy. The big american food companies buy the land and employ the 'survivors' for slave wages and bribe/lobby the governments preventing them to introduce minimum wages and/or environmental laws. In a few decades the lands are destroyed, just like the dust bowl areas in the USA are about to be destroyed. And then, they go forward to the next country.
What else is that than thriving for 'Lebensraum'? Destroying nations without weapons, using money, bribery, international organizations as war machines?