1)
Why did they mention what women used to sing about him?
1.
Radak: Since he has such power, he can kill us to appease his master.
2.
Malbim: He rebelled because he wanted to rule. Also now, he will fight us [and kill more than Sha'ul, so they will sing so again; this will help him to become king! 1 ]
1
Radak (Shmuel II, 15:19): The one whom Yisrael want to make him king, he is called king.
