Divrei ha'Yamim 1 10:14 says that he did not seek Hashem!
Radak: Later he asked from a Ba'alas Ov, and thereby equated this to seeking Hashem, so it is considered that he did not seek Hashem.
Malbim: There it says that he was not Doresh Hashem, i.e. to seek with all his heart and Tefilah. Had he done so, this would have removed the decree (at least temporarily) and he would have been answered. Sha'ul merely asked without Drishah.
What is the meaning of "ba'Chalamos"?
Radak: It is through people who ask [that Hashem answer them] in a dream.
Why did Hashem not answer him through the Urim v'Tumim?
Rashi: It is because he killed Nov, the city of Kohanim.
How could he try asking the Urim v'Tumim? Evyasar had it, and he was with David!
Radak: He sent Sheluchim [to Evyasar] to ask about this war [of Pelishtim].
What Nevi'im did he ask?
Radak: They are Shmuel's Talmidim - "Lahakas ha'Nevi'im Nib'im" (19:20).
Why did he ask first through dreams, and then the Urim v'Tumim, and last through Nevi'im?
Malbim: He did not prepare his heart to seek Hashem, from the most Kadosh source first. Rather, he began with the Kal (easiest), far from Kedushah, which does not need so much preparation.
Why does it say "Gam" three times?
Radak: Each includes the others. This is like "Gam Atah Gam Bincha Gam Ben Bincha" (Shoftim 8:22).
