Jobs was "inspired" by a visit at Xerox labs, they showed him a GUI built using Smalltalk (which they'd also invented). So naturally, he ran back to his office and invented GUI ;)

There is no prize for second… unless you do it better.

Or for third I guess lol Jobs demoed a mac gui to Gates, and apparently Gates ran strait to his Microsoft office, where he too invented gui. Jobs was very upset for years.