1)
Why did he say "Hashem Asher Hitzilani
1.
Rashi (from Esther Rabah 6:10): Hashem did not send the lion and bear for naught. Rather, later I will do so to save Yisrael. Also Mordechai interpreted Hashgachah like this - it is not for naught that Hashem caused the king to take Esther, rather, to save Yisrael!
2.
Malbim: Even though I was weaker than the lion and bear, Hashem saved me via Hashgachah - also now, He will do a miracle for me! Before (36) he spoke according to nature (Kal v'Chomer), and now he spoke based on Hashgachah.
