FORT WORTH, Texas—Brody Malone deleted Instagram from his phone after racing to the lead at the U.S. Gymnastics Championships, an attempt to cut out distractions as he eyed his first national title. Consider it good practice. If the 21-year-old keeps performing like this, the distractions around him are only going to increase heading to Tokyo. Confident from start to finish, Malone overcame a nervous mistake on parallel bars to post a two-day total of 170.700 and stamp himself as the new standard-bearer for the men’s program with the Summer Games just seven weeks away. The victory ended six-time national champion and two-time Olympian Sam Mikulak’s long reign. While Mikulak rebounded from seventh to third, the 29-year-old believes he saw a changing of the guard. “That kid is the future,” Mikulak said. “I’m just this old guy trying to keep up with him now.” Malone said he wasn’t nervous during the …