Looking at this country now ,not all people want to move from the state we are to the next level
I expect that you mean your country is Nigeria, since it is the only country, as far as I know, in which presidential elections are held, which began yesterday, Saturday. Isn't it?
In the Nigerian example, the hypothesis of the candidates' offer to buy votes is very candidate, since there are 18 candidates competing for one seat (presidency). Of course, this falls within the list of political corruption, because a person who works to buy votes from voters to ensure victory means that he is not eligible for that position.
As for the voters, they are also involved in corruption if they accept to sell their votes at any cost.
One of the reasons why people sell their votes is that they assume that their votes wouldn't count. These corrupt politicians have devised means to manipulate electoral results to suit their preferred candidates. Some electoral officials collect bribes from politicians to influence the election results. And this is what is happening right now in Nigeria. Electoral officials have refused to submit the election result to the central server because they have been induced to claim that there is no network. This gives them the privilege of changing the results and sending the fake one to the server.
When people see all these electoral malpractices, they just decide to sell their vote because with or without their vote, the winner of the election has already been predetermined.