Just because it wasn't 1:1 doesn't mean it was illegitimate. Both sides had exactly the same opportunity to cast multiple votes, so neither was afforded an unfair advantage.
As you say, the only reason you didn't continue voting is because you "stopped caring." So Horde had more people who cared more and continued to vote. I know my guild put out calls to vote every day the contest was running.
What's not to believe? Nobody is being lied to. Horde bike got more votes and won.If the voting were tied to battle.net account, the whole process would have at least been believable.