SQL Server 2022 Always On

We have a Windows Server 2022 Failover Cluster with 3 nodes SQL Server 2022 AlwaysOn . Two nodes (Node A and Node B) are in Site 1 and the third node (Node C)is in Site 2.

We also have a File Share Witness server (FSW1) that is also in Site 1.

Node A - is the Primary (Site 1) - synchronous commit

Node B - is the Secondary (Site 1) - synchronous commit

Node C - is the remote secondary (Site 2)used for disaster recovery and is asynchronous commit

FSW1 - is the file share witness server (Site 1)

When we validate the cluster is says we can only sustain a 1 node simultaneous lost otherwise the cluster will down I am confused why this be as I thought as long as you have 50% votes available the cluster would remain.

I my testing if I pull the Nic on Node A or B (not at the same the time) the cluster stay healthy SQL fails over to the other node

If I pull the Nic on Node A and Node B at the same time the cluster goes down despite the File share witness and  Node C being available.

Could someone tell me what I am doing wrong I have the Quorum configuration set to Select the Quorum witness and then configure the file share so the 3 nodes and the witness share should have a vote each.

Kind Regards

Paul