Complex sentence: The rationale at the time centered on the supposedly pivotal role John Larkin had played in supporting Bishop John Ireland's Catholic colonization efforts in southwestern Minnesota; however, little evidence exists that Larkin played any major role.
Split into simpler sentences: The rationale at the time centered on the supposedly pivotal role John Larkin had played in supporting Bishop John Ireland's Catholic colonization efforts in southwestern Minnesota. However, little evidence exists that Larkin played any major role.