#5 To portray RAW as the premier show once again
One of the major reasons for SmackDown Live putting up a terrible showing at Survivor Series is that WWE wanted to portray RAW as the A-show of WWE. RAW has always been the premier show. It is 3-hours long, it has a huge roster, and it features some top-stars like Brock Lesnar, Triple H, and John Cena who draw a lot of money.
But for some reason, the WWE Universe was always invested in the underdog brand of WWE - SmackDown Live. The clean sweep could be a deliberate attempt by the WWE to portray RAW as the prime show, and to remind the WWE audience that SmackDown will always remain a B+ show at best.
In the words of Paul Heyman, "RAW victimised and conquered SmackDown". This squashing however gives the WWE Universe much more reason to get behind the underdog brand.