Covering Palestine first:

Most critical scholars do not believe that Jesus was particularly well-known during his lifetime, and on the contrary, that he was exceedingly obscure. That passage from Josephus is almost universally believed to be at least partially forged by later Christian interpolators and is not regarded as historically reliable.

If anything, John the Baptist was the famous one. Josephus also talks about John the Baptist, in a passage which is not believed to have been tampered.

Now some of the Jews thought that the destruction of Herod's army came from God, and that very justly, as a punishment of what he did against John, that was called the Baptist: for Herod slew him, who was a good man, and commanded the Jews to exercise virtue, both as to righteousness towards one another, and piety towards God, and so to come to baptism; for that the washing [with water] would be acceptable to him, if they made use of it, not in order to the putting away [or the remission] of some sins [only], but for the purification of the body; supposing still that the soul was thoroughly purified beforehand by righteousness. Now when [many] others came in crowds about him, for they were very greatly moved [or pleased] by hearing his words, Herod, who feared lest the great influence John had over the people might put it into his power and inclination to raise a rebellion, (for they seemed ready to do any thing he should advise,) thought it best, by putting him to death, to prevent any mischief he might cause, and not bring himself into difficulties, by sparing a man who might make him repent of it when it would be too late. Accordingly he was sent a prisoner, out of Herod's suspicious temper, to Macherus, the castle I before mentioned, and was there put to death. Now the Jews had an opinion that the destruction of this army was sent as a punishment upon Herod, and a mark of God's displeasure to him. (Antiquities 18.5.2)

So according to Josephus, John the Baptist was drawing such large crowds that Antipas had him arrested and executed out of fear that John might be able to lead a rebellion.

There were other Messianic movements which were more popular than Jesus too. The most popular and (temporarily) successful Messianic aspirant was probably Simon Bar Kochba who was endorsed as the Messiah by the High Priest and was able to briefly retake Jerusalem before finally being crushed by the Romans.

In Palestine and in a Jewish context, the Messiah was, by definition, a national leader and a specifically Jewish liberator from the line of David. He was not a world savior, or really a religious leader, so much as a military and political leader. There was no evangelical message or mission to gentiles expected. Subjugation of other nations, perhaps, but no notion of a soteriological mission. The Messiah was not supposed to save anyone's souls, he was just supposed to save Israel from occupation. As a result, once those leaders were dead, the movements were dead.

The Jesus movement apparently originally thought of Jesus this way too, and evidently (though the history is really hard to recover here) thought he would return after his death as the Jewish Messiah, but Paul, with his mission to the Gentiles, ended up reimagining Jesus, through his own claimed revelation and probably scriptural interpretation, as a universal, spiritual savior. In a sense, he mostly likely conceptualized himself as converting Gentiles not to a new religion, but to an upgraded form of Judaism. Judaism 2.0, no more snipping, and you can still eat lobster.

Simply removing the requirements for circumcision and observance of Jewish dietary codes probably had the most to do with making Christianity much more accessible to gentiles than conventional Judaism.

There always were some gentiles who were attracted to Judaism even in its pure form, by the way. There were gentiles who went to synagogues to listen and even donated money or build synagogues themselves. Jews called them "God-fearers." They worshiped the Jewish God, even monotheistically, but they did not go all the way and get circumcised and become "Jews." Christianity gave them the compromise of just following Noahide law which really helped recruitment. Talking adult men into slicing off a part of their junk was a hard sell, even without throwing "no more bacon" into the mix.