The South has always played a crucial role in the formation of the central Government. Now with Babu going away from the BJP, it has to be seen how things shape up in the near future for the NDA. The TDP has assured that they are with the NDA but it has to be seen how things precipitate in the near future.
The real issue for TDP was that Jagan the YSRC chief has been moving closer to the BJP at the centre as well as the people of the state. The pressure for special status has been building up and all political parties except for the TDP were vocal over this.
Taking all this into consideration Chandrababu and his MPs have thought it fit to go away from the BJP and stay with the NDA indirectly to get the things done, otherwise, it will become a problem for them in the coming elections.
When the Southern parties withdrew the support there are instances in the history when PV Narasimha Rao and Vajpayee lost the power at the centre.
Now for Modi, if Shiv Sena also moves against him it could be a difficult situation. That is the reason Modi was forced to talk to Babu over the phone and suggest him to stay with the Government.
But to keep Jagan away from the BJP and also the people of the state babu had no other option but to pull the Ministers out. By saying that there will be no special status, Modi has also shown his attitude that he cannot be cowed down by the regional parties.