The purpose of the subordinate conjunction 'because' is to answer the question 'why?'
Explanation:
In the given sentence, 'because it was a disaster' is the adverb subordinate clause. The clause begins with the subordinate conjunction 'because.' An adverb subordinate clause is an adverb clause that provides some details about the verb, adjective, or another adverb in the sentence. These clauses are an answer to the 'how', 'when', 'where' and 'why' questions. In the given sentence, the adverb subordinate clause is answering the 'why' question.
