Based on a Naaleh.com shiur by Rabbi Yitzchak Cohen
One can clearly see Hashem through rain. When there’s a drought, people realize that Hashem is in control. Rain is a direct blessing from Him. If it’s not coming down, it’s because of our sins.
Although Hashem does many miracles for us every day, the best proof that He exists is the Torah. In birchat hamazon we say, “Ki ein machsor l’rei’av.” If you fear Hashem, you have no deficiency. Torah brings us to yirat shamayim because Torah demonstrates the existence of the Hashem.
The Gemara says that at Har Sinai the Jews accepted the Torah out of fear. Years later after the Purim miracle they accepted the Torah out of love. Why wasn’t there a complete acceptance immediately at Har Sinai? The Torah is a part of creation. Just as we have no control over creation, initially the Torah too had to be against our will so that subsequently we would look at the world through the Torah lens and recognize Hashem on our own.