Other countries see Charlemagne as a "firewall to block the expansion of Alfheim," and they are willing to help Charlemagne out of its predicament, even risking falling out with Alfheim to facilitate peace talks, and are prepared to provide various aids to Charlemagne afterward—not out of chivalry but as a prudent way of buying safety with money.
As long as Charlemagne continues to exist, Alfheim cannot focus its expansion efforts in other directions. As long as the Elves are not crazy enough to start a war on multiple fronts, the security of other nations will be preserved.
Therefore, Charlemagne must continue to exist, and it needs a proper leader to guide the country against Alfheim.
Maybe someone would say, why not just switch to a puppet?
