The election was between Yeltsin and the Communist party.
The Communist Party were very close to winning, so millions in funds were made available to the oligarchs by Yeltsin and with the blessing of the US, with the obvious but unstated command be "win this thing, or else you're going to lose all of this". The OSCE turned a blind eye to entirely bombed out Chechen villages voting for Yeltsin 100%. Because you know, people typically vote for people who send in the army to destroy their homes and kill their families.
People wonder why Putin is so popular? Mostly because he put the oligarchs in place and, while not being Very Nice At All, didn't pull shit like this.