Complex sentence: James Killian, the MIT president responsible for recruiting Buchanan, described the hire as among the most important and expensive hires he made, because the department's biochemistry division under Buchanan's leadership quickly became widely well-regarded in the field.
Split into simpler sentences: James Killian, the MIT president responsible for recruiting Buchanan, described the hire as among the most important and expensive hires he made. Under Buchanan's leadership the department's biochemistry division quickly became widely well-regarded in the field.