Complex sentence: I initially believed that CCI had done "sloppy" work when I misinterpreted the meaning of edit histories with 2011 dated start dates; in actual fact, CCI seems to have been correct in their assessments of fault.
Split into simpler sentences: I initially believed that CCI had been "sloppy" but found I had misinterpreted the meaning of edit histories with 2011 dated start dates. In fact, CCI seems to have been correct in their assessments of fault.