Complex sentence: For most of the series' run, Raj had not been involved in any lasting romantic relationship, mostly due to his inability to speak to women: however, he is much more successful in flings than the more sexually aggressive Howard.
Split into simpler sentences: For most of the series' run, Raj had not been involved in any lasting romantic relationship, mostly due to his inability to speak to women. However, he is much more successful in flings than the more sexually aggressive Howard.