#1 There are more exciting possibilities with The Fiend as Universal Champion after SummerSlam
The main reason why Bray Wyatt's feud with Braun Strowman has continued for so long, leading up to SummerSlam, is that WWE doesn't have many challengers for Strowman. The Blue brand's roster lacks depth, which leaves the show with a small number of credible heels. Aside from Baron Corbin, Sheamus and Wyatt, SmackDown doesn't have any additional established heels.
The story is the polar opposite with Wyatt as Universal Champion. There are myriad babyfaces on the SmackDown roster, and each of them would love to hold the Universal Championship. Jeff Hardy would make for a formidable challenger. The Fiend could bring out the Enigma's Brother Nero gimmick that fans have wanted to see for so long. Someone like Big E could also prove to be a tough opponent for Wyatt. Drew Gulak sounds like a decent opponent for the demonic monster as well. The post-SummerSlam landscape for the title can be fruitful.
And Let's not forget about Mr. Money in the Bank, Otis, out of the mix. WWE wanted to book Otis against The Fiend at one point in time before Paul Heyman's dismissal. That could become a reality soon if Wyatt wins the Universal Championship at SummerSlam.