The wifi protocol is computationally intensive. The wifi module is effectively a fast 32-bit computer with fairly complex firmware. And then, there's all the RF engineering that needs to happen to make it work.
So, the original thinking was "if you need wifi, we can't price a standalone chip competitively, just buy a SoC". But the genius of ESP32 was that they approached it the other way round: they built a wifi chip, and then figured they can carve out some room for user code. No need to pay for a separate MCU. This worked for a lot of customers, and the economies of scale took care of the rest.
So, the original thinking was "if you need wifi, we can't price a standalone chip competitively, just buy a SoC". But the genius of ESP32 was that they approached it the other way round: they built a wifi chip, and then figured they can carve out some room for user code. No need to pay for a separate MCU. This worked for a lot of customers, and the economies of scale took care of the rest.