It did create a personal computer which was (1) easy to clone and (2) easy to extend with ISA cards. This openness made it a huge success, leading to an explosion of PC-compatible machines.
Most other makers, from Apple to Amiga, vigorously protected their small private markets where they dominated. The original Macintosh has explicitly removed all the expansion capabilities that e.g. Apple II had.
It accidentally made it easy to clone by rushing to market, making false assumptions and hoping the enterprise market would soon lose interest in personal computers.
Rushing to market led to the decision to license the OS from Bill Gates instead of buying the OS or writing it in-house.
An example of a false assumption would be believing that holding the copyright on the BIOS would be enough prevent clones.
Most other makers, from Apple to Amiga, vigorously protected their small private markets where they dominated. The original Macintosh has explicitly removed all the expansion capabilities that e.g. Apple II had.