Itachi knows about the self-destruct how? Zetsu only said that deidara blew himself up, omitting the all important details such as it was 10km wide and warped the fucking SKY.Minato has knowledge of Deidara's jutsu's through Itachi
Minato can't hiraishin 10km or 6+ milesand he takes him out within two seconds with Hiraishin.
Since they're going to think to target a random black ball when there are 8+ S-Ranked Nins running around including pein and mandara.Itachi Amaterasus Deidara while he shapes himself into that black ball of whatever. Or Susanoo just seals him.
Madara isn't there.
How will he with some much crap happening?Deidara will make his speech about how he'll self destruct and how it's art and shit.
You think that itachi and minato will notice deidara turning into a random ball when getting mobbed by several s-ranked ninsYou think Pain and the others are gonna be worried about Minato and Itachi when they're about to get killed too? Either fatty absorbs it all, or Itachi stops it.