Thoughts on why Chase in the backfield never works but Deebo in the backfield does?

[*ochocincos*]

It's all about how often that different player in the backfield actually gets the ball or not.
If they rarely/never actually get the ball, the defense isn't going to worry about them.
If they always get the ball, the defense will hone in on that player.
So the team has to balance giving that player the ball vs using as a decoy.
Also the player has to be effective in the play call too, otherwise it also won't really matter much.