irrational addition of trains by successive RM's.
While there is no doubt on the immense demand that section has (the states you have mentioned have some of the highest population densities in India), without proper addition of line capacity (or in fact, almost zero addition of line capacity) the lines are saturated beyond their carrying capacity.
Add to it old P-way which have TSR/PSR+lack of advanced signalling in many stretches (the aforementioned stretch doesn't come under this though) and you have a perfect recipe for disaster.