#2 Still healing up from impending injuries
There is a saying that the usual dictionary definition of an injury does not apply to sports entertainers. By that definition, they are always nursing an injury of some kind. It is only when they cannot get up and compete from the said injury, that they deem themselves 'injured'.
Braun Strowman has had his fair share of bumps and scrapes along the way and not long ago, it was reported that he was working through some injuries. By not having him in the card, WWE may be affording him a certain amount of time before he heals up to 100%.
Personally, I think that if this is indeed the case, it is a very wise decision because, at the end of the day, Braun Strowman's health and well-being are absolutely paramount. He could come back once again, geared up to cause carnage...