I told you before what happened when the Avengers met the Justice League of America here and here. Eventually everyone realized you’d reallyonly need one hero, Superman, to defeat the Avengers provided, of course, that the Hulk is otherwise occupied-this was when the Hulk had time traveled to WW II and fought the Invaders! Add the motivation of Superman being mind controlled by Darkseid, considered by many to be the ultimate DC Comics supervillain, and you have an unbeatable scenario. So again, Marvel “rented” two DC characters; "Menace from Earth-D" referred to DC Comics and/or Darkseid! They got Jack Kirby, famed for his covers, to draw this one. It sold so well it led to other crossovers including this one and this one. The crossovers continue to this day. 'Nuff said!