I’m confused why the article doesn’t consider the initial question of whether the historical Buddha existed at all. Given the amount of ink that has been spilled over the existence or otherwise of the historical Jesus, and the even spottier historical sources about Buddha (we can’t even nail him down to a specific century), isn’t this question worthy of consideration?
But as I understand it the Buddha is mentioned in a lot of completely independent contemporaneous texts whereas Jesus is basically only mentioned only in the Bible. In itself that doesn't prove anything... the Buddha was active as a spiritual leader for many decades, and Jesus only for 3 years, and maybe the wider society around Jesus was just much more interested in political events whereas Indian society as a whole at the time of Buddha was exploring more spiritual and philosophical dimensions. But I've always had the impression that there are proportionally more history scholars who question the existence of Jesus as a single real person than that of the Buddha.