1 Chronicles 12:32 of the sons of Issachar who had understanding of the times, to know what Israel ought to do, their chiefs were two hundred; and all their brethren were at their command;
Notice that these men of Issachar didn't learn from Scripture what Israel should do; that was pretty well known already. But with Israel in transition between kings, these men knew what Israel should do RIGHT NOW. And because they had this knowledge, God's people were willing to follow them.
Notice that most of the tribe of Issachar only knew that they should follow these men, but even then, they knew what Israel should do. And notice that these leaders were making a change: the kingship had passed form the house of Saul to the house of David.
But other leaders were saying that Israel should be loyal to the house of Saul. How can you KNOW which leaders to listen to?