#2 To make her look strong despite losing the title
Becky Lynch is one of the most popular acts in WWE right now and WWE seems to realise that because they've been treating her like a big deal lately, and rightly so. When Becky turned heel at SummerSlam, she caught lightning in a bottle and her momentum has only increased since then.
With WWE reportedly planning to have Ronda Rousey vs Becky Lynch in some capacity at WrestleMania, the SmackDown Women's Championship needed to be taken off her and was won by Asuka at WWE TLC, with Rousey costing both Charlotte and Lynch.
Becky Lynch throwing Cena out of the ring on SmackDown and then mocking him after the match was WWE's way of making Lynch look strong despite losing her SmackDown Women's Championship. What better way to look strong than to have a 16-time champion put you over?