Basically after all that happened, which pretty much ended the entire premise of the show and what it was all leading to, they needed this crazy break that was something out of Breaking Bad when most of this show is Better Call Saul, especially season one with William Hurt in the Michael McKean deranged genius/lawyer who can't practice law anymore but still runs things role.
Here in this strange episode is a chance where Billy doesn't have to react to what had gone down which would have taken basically a lot of sulking back home otherwise. So this episode does serve a purpose. It makes it so he can be back on track for the final episode, so to speak. Plus, hey, you got John Savage who hasn't been in much, and the Applebees lady's fake laugh is hilarious, as is her and Billy's dialogue halfway through, when things pick up.
