The byzantine generals problem doesn't apply when you have trusted entities.
Except for the minor detail that you never do.
Perfect solutions do not matter.
The only thing which matters is good enough solutions.
For a state (i.e. most states in the current world) federated validators are good enough.
And systems which go beyond that (wrt. byzantine generals problem) have properties states tend to not want.
(I'm not judging if it's ethical good or bad.)
The byzantine generals problem doesn't apply when you have trusted entities.