Complex sentence: The company was founded by Thomas Tull in 2000 and in 2005, concluded an agreement to co-produce and co-finance films with Warner Bros., and began a similar arrangement with Universal Studios in 2014.
Split into simpler sentences: The company was founded by Thomas Tull in 2000. Five years later, Legendary concluded an agreement to co-produce and co-finance films with Warner Bros., and began a similar arrangement with Universal Pictures in 2014.