Why did the Egyptians put taskmasters over the Israelites?
The Egyptians placed taskmasters over the Israelites to slow down their population explosion and afflict them with heavy burdens. This forced labor included building treasure cities for Pharaoh. Despite the affliction, the Israelites kept multiplying, so the Egyptians made their lives bitter with rigorous bondage in mortar, brick, and field service.
Les explains that Exodus chapter 1 says the Egyptians set taskmasters over Israel in order to slow down the population explosion among the Israelites. Those taskmasters afflicted them with burdens, and as part of their slavery they built treasure cities for Pharaoh. Yet the more they were afflicted, the more they multiplied, which grieved the Egyptians. Therefore they made Israel serve with rigor, making their lives bitter with bondage, mortar and brick, and all manner of field service. The king of Egypt also spoke to the Hebrew midwives.
Therefore they did set over them taskmasters to afflict them with their burdens. And they built for Pharaoh treasure cities, Pithom and Raamses.