Question

Why did Stalin want control of Eastern Europe after WWII?

Answer 1

There are 3 main reasons why Stalin wanted to control Eastern Europe.
1.) Russia has historically no secure border.
2.) They wanted to set up satellite countries.  
3.) The Yalta Agreement between FDR, Churchill and Stalin laid out the spheres to influence that each of the allied countries would have, and all the satellite countries all fell under the Soviet spheres.