#2 To avoid any confusions that would've been created if this was a title match
Out of all the things in WWE, one thing that is certain is that The Fiend isn't done with Daniel Bryan yet. Both the Superstars will be facing each other very soon, most probably at Royal Rumble 2020. The company's sudden decision to book a match between Wyatt and The Miz, naturally, doesn't seem to be in line with the ongoing storyline.
Everything happened so instantly that it doesn't seem to be the right match for TLC. There are a lot of confusing questions standing in the way such as Why is The Miz involved in this rivalry? Why isn't The Fiend working at TLC? and, most important of all, where is Bryan?
WWE may have booked Wyatt vs Miz as a non-title match to avoid further questioning from the fans. It'll most likely be a one-night affair between the two and allow the company to focus on the main storyline, that is The Fiend vs Daniel Bryan.