I reckon they ****ed him up when he started playin lots of LO cricket. Not long after he debuted. Went from bowling a length which was awkward at test level to bowling either too short or too full and bugger all in between.
This is quite normal in India, and its a whole process,
1- pick a potential bowler, overhype him after just 1 good match if he does well,
2- If he continues to do well, make him play all the formats, he is paid so much, so there's no point letting him rest, make him work like a dog.
3- He's injured? no problem, let him recover and play the domestic matches where he will bowl 50 overs a week on wickets with no help and poor climate.
4- Oh, the guy is burnt out now, and isn't the same bowler, what next? nothing, the guy gets criticized journalists and everyone else for his poor fitness, lack of commitment etc.
5- and the most important, he gets the tag of an unfulfilled talent, someone who could have done better
The only difference with Ishant is that he is being backed by MSD who thinks he is good enough.