Subject-Verb Agreement (was or were)

The unsold tobacco in the inventories were causing a substantial loss for the state tobacco monopoly. It was mainly made up of tobacco from the east regions.

Is the first sentence correct? Why is "were" used here instead of "was? In the second sentence, why isn't "they" used instead of "it"?

Solution 1:

The first sentence is incorrect. The use of "were" is probably caused by the presence of the plural noun "inventories" immediately before the verb, but "inventories" is not the head of the subject of this sentence. The subject is headed by the noun "tobacco" which is grammatically singular, and which should go with the singular verb "was".