SAT writing section questions question

Hi i just have a few questions that i couldn’t figure out
1)Readers of the novice writer’s recent book have said that it is at once frustrating because of its chaotic structure (but its originality is still a delight).
a)But its originality is still a delight
b)although it is delightfully original
c) and it is delightful in its originality
d) while being so original as to delight them
e)and delightful because of its originality
The answer is E but i don’t get it. Shouldn’t we use a conjunction that contrasts the two( chaotic structure v. still a delight) such as but or although? Why is the answer the one that uses “and”? chaotic and originality as contrasting each other. By the way the parenthesis in the question replaces the underline in the question.

Parallel structure. It is at once adj and adj with opposite meaning. The structure is used to emphasize the contrast between the two qualities of the same object.