How did some MLAs become ministers? Explain.

The majority of the parties elected to the legislative assembly forms the government.

According to the provisions of the Constitution, the ruling party elects its leader, called the Prime Minister, as head of government. 

The Prime Minister, in consultation with the Governor, will form a cabinet containing members of his party as ministers. A portfolio is assigned to the MLA that will be the minister. 

This is where the MLA, who has become a minister now, will be responsible for the entire state of that particular portfolio.