The Yesod Ha’avodah of Slonim zy”a (quoted in Kisvei RaMam) explains this pasuk as follows:
Hashem told Moshe Rabenu, “Do you think that I have treated the Jewish people with the middah of Elokim (middas hadin)? No. I am Havaya. Everything I have done is kind and merciful. Until now, I have dealt with them with hidden kindness. Now, I will reveal My kindness. I will take them out and save them in a way that they can clearly see.”