Yes I agree with you hundred percent that corruption has loomed large in all the states of India. Nevertheless, this is nothing unique; corruption was there in all times and places. Kautilya's Arthasastra for example gives a detailed account of corruption in ancient India, mostly among the government officials as well as the merchants. Aristophanes in the ancient Greece was sharp with his satire against the corrupt political demagogues. In the sixteenth century England, satirists like Hall wanted their compositions to "shoot out sharp quills" like a porcupine to the foibles and corruptions of the society. So it is nothing amazing at all the Bengal in the present day is quite corrupted.
In fact we tend to think that in the good old days there was no corruption and only the present time is very much polluted. There was huge corruption in Bengal during the Sen and the Hussen Shahi dynasties. The upsurge of Chaitanya's Vaishnavism had a purgatorial effect for quite some time; but later with the advent of the British Raj the corruption in Bengal went back to its earlier form. And the tradition continues still today.
Now the question is, who are corrupt? We are. We form the state. We the people of West Bengal are corrupt. How many of us can assert that in our entire lives we have never performed any corrupt ritual? If we purge ourselves, as well as be Good Samaritans and help our neighbours overcoming their shortcomings, Bengal will be a divine abode in no time.