Complex sentence: The first painters to create lithographs at Mourlot were Vlaminck and Utrillo, despite most artists abandoning the one-popular 19th century lithography, during the first part of the 20th century.
Split into simpler sentences: The first painters to create lithographs at Mourlot were Vlaminck and Utrillo. But, lithography, which had enjoyed much popularity in the 19th century, had been abandoned by most artists in the first part of the 20th century.