He was the one who saw Pixar as being a brand (i.e. a modern day Disney) rather than just an anonymous studio. Kids are buying and trusting the Pixar brand not the Disney brand. So to be able to set that all up (e.g. equal billing) required a vision for what the company could be.
Steve was responsible for Pixar. John was responsible for Pixar's movies.
Steve Jobs invested in Pixar because of the hardware. When that didn't fly, the shorts and commercials being done by Lasseter (that paid the bills) turned into a gamble to make a full-length movie. This whole "branding" thing didn't come until the first movie was a success.
Pixar was the success coming from the genius and hard work of three people:
- Ed Catmull for all the tech
- Steve Jobs for the money, the vision through a dark maze and negotiating the first deal with Disney (Toy Story). Yes, he had second guesses, yes, Pixar almost became a division of Philips, etc
- John Lasseter. CalArts. Kicked out of Disney for believing computers were the future, 'hanged in there' at Pixar, as an 'Interface Designer', responsible for giving the human touch to Pixar movies, even the first ones (Luxo Jr, Adventures of Andre and Wally B - pre Pixar) probably helped Steve Jobs 'see the light' on Pixar