Some reports are mumbling that Berlusconi was warned about the risk of attack before the rally by his security team, and he immediately told reporters that he, "almost saw this coming." This wouldn't seem all that strange, except for the fact that the Italian press has scrutinized the security at the event for being inadequate. The PM, who's usually surrounded by a convoy of S.U.V.s and guards armed with automatic weapons, was permitted to re-exit his car immediately after the attack and stand outside of it for a few seconds, unexposed, as this video shows.
There's also the fact that while the assailant has a history of psychological treatment, Tartaglia has no criminal record and has yet to offer a motive for the assault besides that he doesn't really like Berlusconi's politics.
Before yesterday, Berlusconi's biggest problem was his entanglement in longstanding charges of corruption -- his political allies have launched an attempt to pass legislation that would automatically end the corruption trials and clear his name. Bloomberg reported that yesterday's assault and the subsequent "outpouring of sympathy" could help push the legislation forward and end the trials.