“I didn't think it was possible to solve [the double-spend] problem before I read the white paper. McCaleb recalled that process, which took place at a time when Bitcoin wasn’t the cultural phenomenon it is today. The Stellar founder always thought Bitcoin was an awesome idea, but has been bothered by the mining aspect. AuthorBefore Bitcoin, McCaleb thought there was no solution to the consensus problem Bitcoin set out to solve. McCaleb, however, didn’t set out to solve the consensus problem the same way as Bitcoin.

Source: Forbes November 16, 2019 18:33 UTC