why are the indian -eastern coastal plains more wider and leveled than the western coastal plains?

Answer 1

The drainage divide for the Indian Peninsula is located very close to the western coast. It is a great escarpment, the Sahyadri (the Western Ghats), near the western edge of the Deccan Plateau. It is elevated because of a geologic history of uplift relative to the eastern part of the peninsula.
Many major Indian rivers originate in the Sahyadri Range (Western Ghats), and instead of draining into the nearby Arabian Sea, they flow eastward for hundreds of kilometers to the Bay of Bengal.
So the eastern coastal plains have larger drainage basins, more sediment, etc.

Answer 2

Eastern Coastal Plains Of India