Complex sentence: Johnson was pleased with the final episode, although he was concerned that viewers might not understand the "Star Trek" after watching "The Man Trap" owing to differences in characterisation between this episode and the rest of the series.
Split into simpler sentences: Johnson was pleased with the final episode, although he was concerned that viewers might not properly understand the series off the basis of "The Man Trap". This was due to differences in characterisation between this episode and the rest of the series.