2) Russia practically feeds oil and gas and other natural resources to Slavic lands (of course Russia needs money in return).
3) Russia's military capacity (especially strategic) far exeeds any other Slavic army.
1) And that is maybe all, but look at how people in Russia live. Even in 1968 soldiers who came from USSR to Czechoslovakia were so astonished by level of living here that they began to think about why should they occupy this country. Things did not change much since then.
2) That is the reason why Russian economy is big.
3) Strategic capacity is poor, just look at Afghanistan and Chechnya.