MK guy should not have ousted Dayanidhi Maran out of the cabinet. He was the polished and sophisticated guy in the party and could also function as a party spokesperson.
The Maran family actually operates the entire Sun TV network and as far as I know they are also related to Karunidhi's family.
Azhagiri is the first son of MK and there was sibling rivalry between Azhagiri and Stalin, the second son of MK. As far as I know , Stalin is more capable and is given more importance (something like our JD(S) scenario, itself ).
And when Sun Network, which runs Dinakaran daily, that M K Azhagiri was behind the attack on its offices in Madurai, Karunidhi just expelled Maran out of the party. I think it was a bad move and MK could have handled the situation better.