According to backstage reports, the original direction of the Brock Lesnar vs. Jinder Mahal match was to have John Cena as the special guest referee so that he could cost Mahal the match and ultimately lead to a Cena vs. Mahal match where Cena would end up getting the win and the title.
But plans have now changed and AJ Styles will be facing Lesnar at Survivor Series. Because of this, Cena was instead given Styles’ Survivor Series spot on SmackDown’s team since there are no plans for either Cena vs. Lesnar or Cena vs. Styles. This leaves Mahal as the odd man out.
People who needed to be told that the title was changing hands on SmackDown weren’t made aware of this until the day before SmackDown and even then, those same people weren’t clear whether Jinder would be getting it back before Survivor Series, which he is not. So it remains to be seen what the WWE has planned next for Jinder Mahal.

Source: Wrestling Observer Newsletter