Not all controllers are created equal. High-end controllers use more "channels"—essentially data lanes—to talk to multiple flash chips at once. An can be significantly faster than a 4-channel one because it can parallelize tasks , much like adding more lanes to a highway.
While the NAND flash chips do the physical work of storing your files, the controller is the specialized microcontroller that manages everything else. Without it, those flash chips are just a collection of digital "drawers" with no one to organize the socks. What Does an SSD Controller Actually Do? SSD CONTROLLER
NVMe™ Form Factors Blog Series Part II: “NVMe Building Blocks Not all controllers are created equal