#1 To not dilute the Brock vs. Seth feud
Did you incidentally forget that Seth Rollins is supposed to take on Brock Lesnar at WrestleMania 35? I will not fault you if you did so. This is because WWE has hardly focussed on the feud at all, ever since Seth Rollins won the big one. And having Dean Ambrose turn heel would have just diluted the match and distracted from the feud.
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Seth Rollins would have had to focus his attention on Dean Ambrose. And this would have potentially been a bigger talking point than the Universal Championship match. The hype around the big Universal Championship match would have potentially died.
In many ways, with no heel turn, the match was just an ordinary showcase match for The Shield. Well, the WWE Universe was into it and sometimes, that's all that matters, isn't it?
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