That's because Yeltsin set the groundwork for him, in his 93' coup. Where he, as president, dramatically overstepped his constitutional authority, the Russian parliament started making impeachment noises, so he ordered to army to seize it.

The mid-level commanders that carried out his orders were rewarded with wealth and power. The ones that didn't got purged.

Russia came out of that coup and constitutional crisis with all power consolidated in the office of the President.

And you would never guess what happened next!