John Gill Commentary 2 Samuel 20:13

"When he was removed out of the highway, all the people went on after Joab, to pursue after Sheba the son of Bichri." — 2 Samuel 20:13 (ASV)

When he was removed out of the highway
Into the field, and covered over with a cloth, that he could not be seen:

all the people went on after Joab ;
made no stop at all, knowing nothing of the matter, or what had happened:

to pursue after Sheba the son of Bichri ;
these were the troops that Amasa had been assembling, which followed one another after him; for Joab and Abishai, with their men, were at Gibeon first.