There is a well-known difference of opinion as to whether “A new king arose in Egypt who did not know Joseph” means literally a new king, or one who changed his mind.
A new king could have been the result of an invasion and a completely new rule, like when Cyrus of Persia defeated Babylon and created the Persian Empire. Alternatively, it could have been a radical change like when Akhenaten replaced polytheism in Egypt with the worship of one Sun god. It could simply have been the passage of time and ignorance of history. Or just a deranged, xenophobic leader.
Whatever it was, whomever he was, things changed dramatically for the Israelites. Slavery had been the norm in Egyptian society for thousands of years. The pyramids were built with slavery (and technology). But now a once privileged class found themselves to be press ganged into servitude.
But this sudden in change in fortune is another them that runs through Jewish life. Powers have risen and fallen. We have risen and fallen with them. We have in exile always struggled to find favor with our Christian or Muslim overlords. Sometimes we found a monarch, a bishop, an Imam or a Mullah who treated us well. But then fortune changed and the next one persecuted us.
Even now we can find ourselves under a sympathetic president or prime minister or political party and come an election the tables are turned. And we have to live under someone who turns a blind to us or worse. It was so three and a half thousand years ago and it remains so to this very day.