That's what Jim Davis tells everyone. He always cheerfully said he decided to become a cartoonist in order to make money. When asked about anything related to Garfield, he basically always denies having any artistic ambitions. That surprisingly dark comic which suggested Garfield's entire life with Jon was just the hallucinations of him slowly starving to death alone, for instance? Oh, he saw a market survey suggesting the thing people feared most was loneliness, and thought it'd make for a good Halloween strip.

Not to go into an hour long Lasagna Cat speech here, but maybe Jim Davis isn't entirely sincere here?

To me it looks like he made the strip at first to laugh at himself (Jon) and his own cynical tendencies (Garfield). The "I thought becoming a cartoonist was a good way to make money" is an obvious joke at his own expense - it's a terrible way to make money, even with full Snoopy-level merchandising.

It's also notable that he's been very positive to people doing weird things like Garfield minus Garfield. He's not at all possessive to his creation. He accepted ages ago that as the comic became a phenomenon, it wasn't wholly his anymore.