I don't know if war is needed to destroy forts???
If so, that is the first step. Next, just send a army with a hero there and attack the castle (just life capturing a city if you will). After you've captured the fort, it will auto-demolish in 4 hours. at the time of capture, you need to build a mark tower in that contour, and move a city (owned by the would be owner of the future fort there) inside the contour. Or, the owner of the would be future fort can capture a town inside that contour if you do not want to spend gold by moving a city. after you have a city inside the contour, place another mark tower where the previous fort was. wait 24 hours for the tower to finish, then go inside the tower and select, build fort for 500 gold.

take note of these rules:
from build #1417 Here
New contour system is implemented from scratch:

You can now put a mark tower if:

Position of mark tower is not inside any contour
You have a city inside a contour, where you want to build a mark tower
You have a permission to make changes inside a contour from fort owner

You can now build a fort following these rules:

Your water border is continuous and your mark tower locks it into a contour;
You have at least 1 normal city inside;
You have an ally relationship with fort’s owner, which exit is being closed by your contour, in case you connect your contour’s water with his.
You have an ally relationship with the owner of some contour and the permission to build on his land, inside which area you are planning to build a fort and you are using his water.
You have an ally relationship with the owners of all the contours blocking your way out and you are using their water.

You can transfer a city to a contour if you are allied with all the fort owners that stay in path from the current city place to the new city place in the target contour. This means you can transfer a city from an enemy contour without any restrictions.
Added morale penalty with the following rules: For each 10,000 units in one cell morale of all armies in this cell is reduced by 1%, but it will not go less than 25%. Details
Logs are activated again (when having more than 20 players), additional grouping method is added – during massive battles you will see only commander to commander damage, instead of army to army.
Diplomacy changes: Order diplomacy rules are now superior over your personal diplomatic relationships. Details

Do you use the 4 hour window to demo the resource points and get gold?

vassal reports no gold received after fort was destroyed the only thing he got was the resources stolen before the fort was destroyed

We did not know of the above and he did not have a screen shot of the just captured fort. Will support still give him consideration?

Aachen
Also please note, that reward for forts is switched ON not for all servers. New servers: Koryo, Skogmark, Albion will be activated later.