1)
Why did they call him "Melech ha'Aretz"?
1.
Rashi: There was a stipulation between us - "if you can strike me, we will be your slaves" (17:9). You need only to descend from your throne, and he will be king of this land!
2.
Malbim: They suspected that he came to spy. It cannot be that he fled, for he is Melech ha'Aretz (of Yisrael)! He is greater than Sha'ul. The nation considers him to be king, and also due to his strength. He is also king of Eretz Pelishtim, due to Galyus' stipulation. He came to strike us!
