Does not this sentence require contrast? Chocolate had been

No a contrast is not required here.
The purpose of the sentence is to inform the reader that chocolate was once a luxury and it may be a luxury again. A contrast would have been appropriate had the sentence mentioned that chocolate was once a luxury but is no more so. Hence, contrasting ideas are not mentioned in the sentence. In fact, the sentence is just two separate sentences joined by the conjunction 'and'.

Two separate events in the past, one happening before the other, are not discussed in the sentence. That is why past perfect tense is not required. Simple past tense would do. Thus, "had been" in options A and C is wrong.
Because a contrast is not required here, option B is also wrong. Option E also uses the word 'although' which introduces a contrasting scenario, which is not the case here. Thus E is wrong.

Option D correctly uses the Simple Past tense 'was' to state the past about chocolate. It also uses the conjunction 'and' to join the first part of the sentence with the second part, which states that the cocoa shortage may make chocolate a luxury item again. Thus, chocolate is back to its "luxurious" status again and thus, there is no contrast.

Hope this helps.