Without "them" in C, the sentence is not even complete.
One way to think about "in that" is that it expresses specific information to elaborate on a general statement.
For e.g. Humans are mammals in that they are warm-blooded.
"In that" explains "in what way" humans belong to the general category of mammals.
Back to the question. First, the antecedent of "them" is unclear.
Let us assume that "them" refers to the correct antecedent. Now ask whether "in that" makes sense.
"The company's troubles are the result of X problems" in that "Y attempts have failed to correct the X problems".
Here, does "Y attempts..." explain how or in what way "the company's troubles are the result of those problems"? To be able to explain it, the attempts would need to have come first. But the attempts to correct can only have come after the problems were discovered, not before.
In this question, the sequence of events is more like this: Stagnation/missteps/blunders -> troubles -> attempts.
At best, the two threads provide independent pieces of information. "In that" incorrectly links them.
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