Is the implication here that a bunch of Jewish people started pretending there was a guy named Jesus and that he was the messiah, and pretending that he lived a few decades back, and that's more plausible than people following a charismatic leader and deifying him after he died?

Thats literally not true. It provides multiple non-christian historians (Tacitus, Pliny the Younger, Josephus). Theres all kinds of charismatic leaders today that people ascribe religious meaning to, I'm not sure why some people have a hard time believing a charismatic dude had followers who believed he was god.