Political reasons only which in other words we call selfishness or being oportunistic...the problem with congress cannot be a reason...if it was then he must have gone independent like his father rather than joining 

Problems with congress due to political reasons gave BJP a cue to influence Scindia towards them. 

Nobody would like to stay on a sinking ship that is congress. No leadership. No willingness. No direction. And then when BJP, the juggernaut at present, come knocking at the door, you might not agree at first but surely think at least. And there is the loophole. That is where BJP's attack targeted. They offer you posts and other perks such as protection from the law, image proofing, freedom of overt speech etc. Seriously who wouldn't desire all this being a politician. 

BJP is using the loopholes to get the mandate i guess. They have done it in Karnataka, and now MP. maybe they will target Rajasthan (Sachin Pilot) too.