1 Chronicles 12-14

In 12:32 the statement is made about men of Issachar who "had understanding of the times, to know what Israel ought to do....." When it was made know that king Saul and his sons were dead these men of Issachar were moved by God to act. Maybe they looked back to the times of the judges as saw the lawlessness of Israel when they had no king. Maybe they considered how Saul had elevated himself and neglected the pursuit of God. Whatever their reasoning they understood that it was time for David to be proclaimed king of Israel. And that was their purpose in coming to Hebron.
It took me about 12 minutes to read this passage.
Stuart