Why are so many famous classical composers from Eastern Europe?

You need to do more research before making that assumption.

because classical music ******* originated from europe

The only composer you mentioned who's from eastern Europe is Chopin - and he left Poland aged 20 and never returned. Germany and Austria are either western or central Europe.

The reason that "every" famous classical composer is "born within a 300 mile radius" is because you have left out all the ones that weren't. Perotin, Tallis, Monteverdi, Tchaikovsky, Verdi, Grieg, Shostakovich - plenty of others to choose from.

As for why they were born in Europe - it's hardly surprising that the masters of European Classical Music were born in Europe is it?

i am a career professional classical musician and music theorist.  As proud as I am of my Polish heritage (and Polish was my first language) I have to tell you that your assumptions are just perpetuating the close-mindedness of previous generations.  It's a big world out there, and yes - there were centers of respected music that attracted people from all over the world - but many of them them returned home to pollinate their own cultures. As travel and communication improved, the process was faster.  Now - no boundaries.  You could choose any field of endeavor, and find locations that attract talent.  There is a baseball camp in the DR that only teaches knuckleballers.  So?  Is that magic, and are they all going to stay there?  Of course not. Not long ago, there were no black prima ballerinas, and all dancers ran to Russia to study.  Things change.  I will not burden you with a huge list of composers that prove your thesis wrong - but you need to get out more.  (Typos repaired - sorry.)

And Chopin is the only one from Eastern Europe, or he was at least born i Poland, but his father was french and he moved to Paris at the age of 20... the rest is from the west...  =)

But sure, there are other guys like Tchaikowski, Dvorak, Rachmaninov and Smetana.

Germany is usually not considered eastern Europe.    https://www.google.com/search?q=eastern+europe&rlz...

You forgot France, Italy, and Spain.