(using the name Judas for the betrayer was perhaps a subtle shot at Judas of Galilee).
For Mark's audience, I think that was as subtle as a 2x4 between the eyes.
His audience would have been well-versed in all of the literary works Mark referenced, and they would have been painfully aware of the religious, political, and historical context in which Mark wrote.
I think Mark was satire, and I expect it was greated with enthusiastic laughter by his audience.
Consider:
- he portrays the apostles - who have the same names as the 'pillars' of the Jerusalem Church that led Judea to disaster - as blundering blockheads
- he implies that Pilate, apparently one of Judea's most brutal and unpopular governor's, was nowhere near as bad as the Sanhedrin
- the Sanhedrin, the learned men of the culture, are portrayed as not understanding their own religion
- giving the name of Judas to the betrayer, as mentioned
- the Roman centurion being the one to recognize Jesus as the Son of God is clearly a bit of absurdity
- Jesus' death resulting in the temple curtains tearing is if anything a bit anticlimactic (and might even be taken to have a bit of a prurient overtone)
- even the framework of the story, the reworking of Caesar's life into a silly story about a wandering miracle worker and his band of merry dunces, is a classic comedic tactic ("first as tragedy, then as farce")
Mark absolutely skewers his opponents, and once you understand all the context, it's actually really, really funny. Deeply irreverent to every single sacred cow of Mark's opponents, but not in an angry, accusatory fashion so much as a tone of savage mockery. It's even possible that being written in bad, colloquial, romanized Greek was part of the gag; humorists are known to sometimes adopt such a tactic.
That probably explains its popularity, too. It seems to have spread quite widely and rapidly through the Christian community. Humor is an extremely effective means of distributing propaganda, as demonstrated by the success of memes in the modern context, as a tactic for waging cognitive insurrection against TPTB.
It doesn't take long for humor to stop being funny, though. Since most jokes rely on shared context, word play, subtle allusions, etc., they get lost very quickly. Most of the humor in Shakespeare's comedies goes right over a modern audience's head, especially if you just read them.
So, my take here is that Mark was basically pointed satire, written for a very specific purpose at a very specific time; that it achieved its goal brilliantly and therefore became an "underground hit"; and was then in turn subverted by Matthew and Luke who historicized it, thereby removed the humor (changing the genre from comedy to tragedy, really), and thus reasserted Judaizing influence over the church.
Life of Brian was actually closer to the spirit of Mark than any of the subsequent gospels.