What’s the importance of bearing that in mind?
What's more likely is that Schulz would simply have started a different chain, and we'd be talking about that company the way we do about Starbucks now.
The focus is not on the other bidder (who may or may not have gone on to make a fortune).
The point is the seller could have gotten more than what Schulz paid for the chain. If this was a corporate m&a situation and a second bidder arose at a higher price, the board has a fiduciary duty to consider that offer.
So he was a billionaire or a soon-to-be billionaire.
(Starbucks also used to be a lot more, well, serious about coffee, selling fresh-roasted coffee in bins in the store rather than bags shipped out from central roasters, as well as selling a small but well-curated selection of brewing equipment that wasn't just Starbucks-branded stuff. Peet's still has some of that vibe, although they're less eclectic now than they were even 15 years ago.)