GMAT Sentence Correction (SC) | Just unable to understand this sentence: Regarded by

"Their" refers to "sales".

However the modifier before "sales" seems to be severely problematic to me.

Regard X as Y: X should be parallel to Y.

Here X = Sales - noun
Y = increased by international tensions during the Cold War - past participle phrase modifier of X ("sales")

X and Y are not parallel and Y is a modifier of
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