Arizona is 2-7. They have a rookie head coach. Their rookie quarterback has 6 touchdowns and 10 turnovers. As a team, they are averaging 14 points and 236 yards a game. Despite all that, they opened -3 and are now -5. The line could reach 6 or even 7 points.
Arizona's only wins this season have come against 2-8 San Francisco. In both games, the 49ers were using a backup quarterback and Arizona needed five Frisco turnovers to win the first one. Aside from that first Frisco game, Arizona has scored 18 or less points in every contest this year. Yet the spread score for this game now has Arizona winning 23-18 (Arizona -5, total 40.5).
Football players don't like being publicly humiliated. Neither do the coaches. For Oakland to lose here would be the ultimate humiliation.
Oakland tanking? Leave that to the flat earth/scripted games brigade. The Raiders will come to play. It might not be enough to win, but if the line keeps climbing they might not have to win in order to cash.