These countries have GDP much bigger then India and don't have poor people, Japan and Saudi Arabia are very rich countries they can spend few Billions in defense.
Nonsense. Just because a nation is rich does it mean that it has to buy weapons even if it does not need them as it does not face any tangible threat? Totally illogical. Some of the reasons I can think of for this abnorma behaviour are as follows:-
1. Surplus funds available, so buy expensive toys, example, Royal family of Saudi Arabia. After all aren't the latest edition of F-16 better than flying hawks/falcons which kill pegions? Or camel races?
2. Yes, US security umbrella exists. It has worked so far but who knows the future? Example Japan.
3. We have no real threat now, now that the Soviet Union is gone. But we were strong and powerful once with colonies all over the world... sob.. sob.... The Yanks are showing off again, after all some one has to stand up and lead Europe. Example Germany, Italy, France.........
4. Russia:- Leningrad has got back its historic name 'St Petersburg', But Peter the Great is long gone and so has the Russian Empire. The Americans continue to encircle and pincer and probe and generally make a nuisance of themselves. The economy isn't that great. People are happy only with Vodka. What to do? Hang on, didn't Orwell have something to say about that? Yes, he said War is Peace. War diverts people's attention, unites them, brings peace at home. And an unipolar world is unthinkable, right? All said and done, look at history. Duke of Wellington just served the coup de grace, it was Russia that defeated Nepolean. It was Russia which defeated Nazi Germany(Stalingrad-1942). She will rise again, have no doubts.
5. USA:- The 'rightful descendants' of the Greek, Roman and British empires. The flag bearers of the European civillisation with pretentions of being the harbinger and facilitator of world peace feels that it is the 'Last man standing' in the chaotic world where European allies have fallen by the side or deserted her and only the Anglo Saxon ties remain. On her way down with more enemies than friends but will remain a power to reckon with in our life times and those of our children.
6. China:- Not a rich country. Sould have been born in South America or Africa where she would have automatically been 'boss'. Asia has too many bosses to start with, Russia, Japan, South Korea, Taiwan, Pakistan and India. Being a regional power here is tough, too much competition. On her way up as she has adopted Human Wave tactics to industry and business. Floods the world with cheap and unreliable goods in huge quantities.