We have that problem too, a lot of the corruption (I'd say most but I don't have data) is to gather money to be used by the political parties on their campaigns, propaganda, etc. Buying voters with literal cash works with people that are very poor and mostly alienated by the government.

As voting is compulsory in Brazil, a lot of people vote on the person that appeared on the television, or the person that had pamphlets being distributed at the red lights, so spending money on campaign works, indirectly buying votes.