Answer by taking a quote from the following article:

Wayne Coleman was born into a working-class family in Phoenix, Arizona on June 07, 1943. His father was from Mississippi, and his mother, of Cherokee ancestry, was from Arkansas. Coleman was attracted to weight lifting in the fifth grade. As a teenager he was an avid reader of bodybuilding magazines, his idols being Steve Reeves and John Grimek.

Graham returned to the WWWF in April 1977 after an agreement with promoter Vincent J. McMahon (Senior). Graham defeated Bruno Sammartino for the WWWF Heavyweight Championship on April 30, 1977, in Baltimore, Maryland. Graham held the title for nine and a half months. During his reign, he wrestled across America and in Japan (February 1978), facing challengers such as former champion Bruno Sammartino, Jack Brisco, Dusty Rhodes, Pedro Morales, Don Muraco, Mil Mascaras, Strong Kobayashi and Riki Choshu. On 25 January 1978 in Miami, Florida at the Orange Bowl football stadium, Graham wrestled against then-NWA World Heavyweight Champion Harley Race in a WWWF World Heavyweight Championship vs. NWA World Heavyweight Championship unification match which ended in a one-hour time-limit draw. Although a defeat by Bob Backlund, who was to embody the virtuous junior "all-American" wrestler, had been written into Graham's current contract with the WWWF, Graham suggested another outcome to McMahon: that Ivan Koloff should turn on him, thus starting a feud that would make Graham a fan favorite. McMahon refused because of the handshake deal to make Backlund the new fan favorite champion and he did not want to go back on his word. It was also unheard of for a counter-cultural character like Graham to be a fan favorite, because McMahon and many old promoters saw Graham as a confirmed heel and therefore a negative role model. Graham eventually "lost" the title to Backlund on February 20, 1978. Another feud Graham had as champion was with Dusty Rhodes, which culminated in a Texas Bullrope match. His confrontations with Rhodes continued after Graham had been forced to drop the belt to Backlund. Rhodes himself, a long-time friend of Graham's, recalled these matches with Graham in 1978 as among the most exciting and memorable of his career. Disillusioned by the premature loss of his belt, Graham left the WWWF in December 1978 and accepted an offer to join Paul Boesch's promotion in Houston, Texas, lending himself out for other NWA events in California and Florida as well. In April 1979 he embarked on his third IWA tour of Japan, where he wrestled the same men he had worked with in 1974. In March 1979, the new Continental Wrestling Association (CWA) named Graham as their World Champion. On November 8th, 1979 Graham lost the belt to Jerry Lawler in Lexington, Kentucky. His following NWA engagements in Kentucky, Tennessee, Georgia and Texas became fewer and rarer until he stopped wrestling in April 1980. Graham wrestled only two matches (one in Canada and one in Los Angeles) in the whole of 1981. He spent some time competing in Japan, where he added some martial arts techniques to his repertoire. CANNOTANSWER

Why did he return to the WWWF?

an agreement with promoter Vincent J. McMahon (Senior