Word of the assassination attempt spread like wildfire throughout the Fire Nation. Outrage and fury rose up from the commoners- for an outsider to dare to strike at the Fire Lord was unforgivable- inconceivable- the first such attack in all recorded Fire Nation history.
The next step was clear- and inevitable. If a Fire Lord can be attacked, then the Fire Lord is weak. If the Fire Lord is weak then the Fire Lord cannot be the Fire Lord. It follows that the Fire Lord may not be the true Fire Lord- but an imposter.
Needless to say- fake Fire Lord's were generally frowned upon in the Fire Nation. So much so that peasants were generally inclined to revolt and initiate a slaughter so merciless that it would be removed from official Fire Nation history at least twice as quickly as the assassination attempt that triggered it.
Adding fuel to the fire was Admiral Fie Pon Leh, who having received news of vulnerability in the new Fire Lord's rule, had chosen to halt the already slow withdrawal from Earth Kingdom territory of the large number of Fire Navy ships that were presently under his command.
Fie was a member of the Pon Leh family- whose history was vague and unremarkable. Despite no one having any clear understanding of when the Pon Leh line actually entered Fire Nation upper society, or what they had done since, there was a strong and unified feeling of mild distaste concerning the entire line.
Faced with a lifetime of unending shunning and the inability to correct wrongs that no one could recall- Fie had become bitter and angry. This was not helped by being put in charge of things that blew other things up- he might have benefited more from a nice job in a greenhouse perhaps- we'll never know.
Despite Sokka and Toph having made a fairly unremarkable escape from captivity by this time- no one in the Fire Nation or in the navy was entirely sure what exactly the Earth Kingdom was doing. Admiral Pon Leh proposed the only reasonable course of action. To unite under the only true remaining member of the royal line- Fire Lady Azula- and to resume hostility against the shattered Earth Kingdom settlements.
Fire Lord Zuko was displeased.