Joe did win his WWE Championship match with AJ Styles on Sunday, but only via disqualification which means the title doesn't change hands. The DQ occurred after Joe taunted AJ's wife and child who were ringside; Styles snapped, tackled Joe through a barricade and struck him with a chair, costing him the match.
Mike Johnson on the latest episode of PWInsider Elite Audio claimed that WWE thought about putting the championship on the Samoan Submission Machine, but didn't go forward with it, saying:-
"There was consideration for Joe winning the belt but obviously that's not the final finish they went with."
No reason was given why the company changed their minds, but the ending they elected to go with does seem to make sense in storyline. The feuding between Styles and Joe shows no sign of stopping and was exacerbated further following Joe attacking Styles on SmackDown LIVE this week, where he choked the WWE Champion unconscious.
A rematch between the two at next month's Hell in a Cell pay-per-view seems logical, would be highly anticipated by fans, and arguably merits the 'Hell in a Cell' stipulation as Joe looks to claim the WWE Championship from Styles.