The problem with Athrongism becoming a thing is that Athronges was (probably) not leading a Messianic movement. He was a small scale outlaw. Social banditry was commonplace in first century Judaea, as both the Herodians and the Romans were viewed as illegitimate leaders. In the same time period, Judas the Galilean also led a revolt, one that had more impact than Athronges as Judas' movement lasted 60 years and sparked the formation of the Zealots.
Christianity succeded so wildly because Paul set it on a course to proselytize to gentiles. Jews of that time period were leery of messianic candidates. So to get Athrongism to become popular I would recommend that he claim to be a prophet, like Thaddeus or the unnamed Egyptian in Acts. He could call for the reinstatement of the Jubilee in an attempt to free the slaves and cancel debts and land transactions. He writes down a book of prophesies reminiscent of Isaiah or Jeremiah, and hopefully continues to prophecy until Judas' revolt.
Judas is more successful, not implausible as Varus could be quite incompetent (cough cough Tuetonberg forest) , so the shiny new Temple is destroyed earlier than OTL, and Athronges gets vindicated. His book is incorporated into biblical canon. The Temple is rebuilt again, which it will be because the political reasons the Flavians had for promoting their destruction of the Temple won't be present during Augustus' reign. Athronges probably is put to the death before the Temple is rededicated and his brothers and supporters enslaved and exiled, but he is acknowledged as a prophet.
Judaism spreads through the Empire, faster than OTL, and Athronges works get spread by his enslaved supporters to their fellow slaves. Pagan Romans in dire circumstances, the underclass of slaves and debtors, are particularly attracted to Athronges' teachings. Over the next few centuries, Judaism becomes more popular in the Empire, with Athrongism emerging as a leading sect. It becomes dominant when Athronges martial aspects are emphasized and it becomes the religion of the Legions.
Athrongism's emphasis on equality of birth and relative egalitarianism makes it more politically useful than Sadduceeism or Pharasism for ambitious generals of low birth. A perfect storm brews, and a freedman Athrongic Emperor ascends in Rome. He purges the Senate and frees slaves as a show of faith, but is more concerned with cementing his religious monopoly. He persecutes all the other branches of Judaism, and firmly grasps control over the Temple. This sparks a war, and eventually the Emperor decides not to bother with the Temple in Jerusalem, he'll build his own in Rome.
This breaks Athrongism from the rest of Judaism.