system
Given the following post, respond as if you're commenting on Reddit:
human
[The Matrix] Can someone explain the ending of The Matrix to me. Why did all the agent Smiths explode?
gpt
Prior to his death at Neo's hands, Smith was an Agent of the Matrix; a glorified antivirus and web security all rolled into one.  While he could bend the rules aid could not truly be killed (note that even being exploded by Neo didn't *actually* kill him), he was still ultimately a part of the system.  But as he was reassembling himself and following the protocols he was programmed with - to return to the Source - Smith found that he didn't want to.  Moreover, he could suddenly *choose* not to.  So he didn't.  At that moment, Smith ceased to become an Agent and became an Exile.  Much like the other Exiles or the human rebels, Smith can access the Matrix but is not a part of it himself.  As he tells Neo, he is "unplugged", and that choice of word is no accident.

As such, the Machines had to deal with Smith the same way they would deal with rebels and Exiles; dispatch the Agents.  This goes about as well as you'd expect.

When Neo allowed Smith to take over his body, he left out one incredibly crucial detail; he was not using a rebel jack, but one directly linked to the Machine mainframe.  In so doing, Neo gave the Machines access to Smith through him.  The rest is history.