Retailers reported moderate gains in their November sales, as much because of their sales of a year earlier being so bad as that shoppers were getting a head start on buying their holiday gifts.

a.
b. of their sales a year earlier having been as bad as because
c. of their sales a year earlier being as bad as because
d. their sales a year earlier had been so bad as because
e. their sales of a year earlier were as bad as that

my thought was.. as much because of X as because of Y.

is b and c wrong because if they use OF, then the 2nd because needs to be followed by OF. and since it doesn't we can eliminate B and C? is this thought process correct?