Accepting Hashem's authority is difficult

I had another take on the difference between the two times that Moshe came: The first time, they took his word naturaly, like anyone in a dire situation that grabs onto any hope. Hakadosh Baruch Hu didn’t want our Emuna do be based on something like that. Therefore, he purposely sent Moshe at that time although he knew that it would backfire. This dashed all natural grasping-on-hair hopes. Now, Emuna was something to be learned and acquired. This Pshat can be read into the Pasuk as, and they didn’t listen to Moshe out of short breath and hard work [like last time].