Jamieson, Fausset and Brown on 2 Samuel 20:11-13

11-13. He that favoureth Joab, and he that is for David, let him go after Joab--It is a striking proof of Joab's unrivalled influence over the army, that with this villainous murder perpetrated before their eyes they unanimously followed him as their leader in pursuit of Sheba. A soldier conjoined his name with David's, and such a magic spell was in the word "Joab," that all the people "went on"--Amasa's men as well as the rest. The conjunction of these two names is very significant. It shows that the one could not afford to do without the other--neither Joab to rebel against David, nor David to get rid of Joab, though hating him.

2Sa 20:14, 15. Joab Pursues Sheba unto Abel.