Intel initially didn't plan on having fast IA-32 performance. The IA-32 part of the chip was called the "IVE" which was short for the "Intel Value Engine." The thought was that it was enough for the chip to boot in IA-32 mode to be compatible and it was expected that you would set up system state and jump to 64-bit mode as fast as possible. So really it was just meant for compatibility. I imagined it was just a dusty corner of the chip using some old 486 core to take up the least amount of space.