Marbles - real name Jonathan May-Bowles - was charged with causing harassment, alarm or distress in a public place for accosting Murdoch during Tuesday's Commons culture, media and sport select committee hearing.
The activist has now explained his motivations in a Guardian article, claiming that he didn't target Murdoch in order to achieve fame.
"If you're of sound mind, you might quite reasonably ask what possessed me to smuggle a shaving foam pie into Portcullis House and throw it at (though, alas, not into) the face of one of the world's richest and most powerful men. I didn't do it because I wanted more Twitter followers. Simply put, I did it for all the people who couldn't," Marbles wrote.
He charged that Murdoch's media firm News International is "one of the most insidious and toxic forces in global politics today", adding: "The phone hacking scandal, despicable though it is, barely scratches the surface of the damage done by News International."
Marbles admitted that even as the committee hearing got underway yesterday, he was unsure if he'd actually follow through with hurling foam at the News Corporation head, but soon realised that he'd be forced to act as "committee member after committee member feebly prodded around the issues".
As he sprung into action, Marbles said he found himself unable to shout a planned "wave of polemic" at Murdoch, but was ultimately satisfied to have at least publicly chided the mogul as a "naughty billionaire".
Marbles was grabbed by Murdoch's wife Wendi seconds after he'd thrown the foam pie and was eventually escorted from the building by authorities and taken to jail.
His incarceration led Marbles to reflect on the event and he now wishes to make clear that his actions weren't inspired by hatred for Murdoch.
"Maybe what I was trying to do was remind everyone... that he is not all powerful, he's not Sauron or Beelzebub, just a human being, like the rest of us, but one who has got far too big for his boots," he added.
Murdoch denied any wrongdoing during his testimony before the committee and claimed that he'd been let down by "people [he] trusted".
A live stream of yesterday's hearings on the News of the World phone hacking scandal attracted more than 1.5 million viewers, with viewership increasing by 25% after Murdoch was attacked by Marble's foam pie.
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Watch Jonnie Marbles strike Rupert Murdoch with a foam pie below: