What were the major concerns of the Muslim League?

Their main concern was to make sure Muslims had a voice, essentially.

The Muslim League rose in response to the Indian National Congress, which, while not a Hindu organization, was made up of primarily Hindus. Some Muslims wanted to make sure that the Muslim voice wasn't overpowered and that the INC would not go unopposed, so the Muslim League was formed.

Over time, the two parties became more divided, with fewer and fewer Muslims appealing to or voting for the INC.

There were some causes they rallied behind at various points, but generally speaking, they just existed as a political voice for Muslims to oppose the Hindu majority.