He did it as a joke, and to illustrate what a sham the system is...
Stephen Colbert Wins Democracy!
Kingmaker Pundit Regains Super PAC, Files Financial Report, Takes Nap
"Colbert Super PAC has brought in a staggering $1,023,121.24, which my accountant explains to me that is a number far above 'one,' 'two,' 'five,' or even 'many'" said Stephen Colbert, President and Returning Champion of Colbert Super PAC. "We raised it on my show and used it to materially influence the elections – in full accordance with the law. It's the way our founding fathers would have wanted it, if they had founded corporations instead of just a country."