New king in town

Exodus 1:8-10 - Then a new king, who did not know about Joseph, came to power in Egypt. "Look," he said to his people, "the Israelites have become much too numerous for us. Come, we must deal shrewdly with them or they will become even more numerous and, if war breaks out, will join our enemies, fight against us and leave the country."

I wonder how this new king could "not know about Joseph." Did he maybe not want to know about the history of the Israelites? Didn't the king(s) before him all know? Wasn't this king taught about Joseph in history class? Where did he think the Israelites came from? Why did he think they were there? Did no one explain it to him? Or did he just not want to listen?

The king made at least 3 huge assumptions:

1. If he did nothing, the Israelites would increase in number.
2. The Israelites would fight on the side of Egypt's enemies.
3. The Israelites would leave the country after a war.

Assumption #1 is fairly reasonable.

Assumption #2 is not. I wonder why he thought they would fight on the side of someone who was attacking what had been their homeland for 400 years. Perhaps he saw them as a subversive power, but what reason he might have had for this is not obvious.

Assumption #3 is perhaps his real reason for action. He seems to want to keep the Israelites in Egypt. They were probably good workers in general and had become a significant and important part of the society and economy. Losing them could be disastrous. If this was something he was worried about, then I wonder why he took the action of turning them into slaves with harsh masters. Wouldn't that have the opposite effect from what the king wanted?

I wonder if this wasn't all the king's idea. Did he have lobbyists pressuring him to contend with?