וַיָּקָם מֶלֶךְ חָדָשׁ עַל מִצְרָיִם אֲשֶׁר לֹא יָדַע אֶת יוֹסֵף
A new king arose over Egypt, who did not know about Yosef
The Gemara relates a machloket about this between Rav and Shmuel, one said that it was a literal new king, and the other said that it was the same old king with a new attitude. According to the opinion that there was just a new attitude, this is quite perplexing. This same Pharaoh, to whom Yosef told that he can only interpret his dreams if Hashem allowed it, comes back and says to Moshe “Who is this ‘Hashem’ that I should be listening to what He commands.”
Rabbi Meir Rubeman writes that ingrates earn a special dose of Hashem’s wrath. The reason for this is that one who doesn’t show gratitude to others is similar to a heretic. Heretics are simply high-level ingrates. The One who gave them life and everything else they have, is simply a non-entity to them. Though one may start with a low level ignoring of small favors, he may end up ignoring the big ones.
Pharaoh started with ignoring the good that Yosef did for him. Everyone knew Yosef, he was the hero who kept the world alive through a terrible famine, yet somehow Pharaoh “did not know about Yosef”. He refused to acknowledge him. This led to the later “Who is this ‘Hashem’ that I should be listening to what He commands.”
Conversely, actively acknowledging good from others will lead to greater gratitude toward Hashem. We say three times a day (in modim) that we thank Hashem for “the miracles that are with us every day, and the wonders and goodness which are our constant companions.” As long as one’s sense of gratitude is not dulled, a great awakening to what we truly owe Hashem can come about.