Complex sentence: Despite having spent several years excavating there, Hewett never published a detailed account of his research at Chetro Ketl; however, much is known about his work at the site through thesis and dissertations written by students who worked with him.
Split into simpler sentences: Despite having spent several years excavating there, Hewett never published a detailed account of his research at Chetro Ketl. Despite this, much is known about his work at the site through thesis and dissertations written by students who worked with him.