It's not hard to imagine an alternate universe in which we all have RISC workstations with the equivalent of ME, and Intel/AMD are the minorities who have more "open" CPUs without, but only because they hadn't grown enough.
The underlying reason why ME became popular is the same reason why proprietary walled gardens became popular: because they are heavily promoted as a security/safety feature, and "who doesn't want to be safe and secure?"
Remember that, shortly before the turn of the century, Intel was convinced by the masses to remove a feature that would seem almost innocuous today, a serial number, but only because they marketed it as for DRM/identification instead of a security feature: