Srk700 posted...
Byleth doesnt know Edelgard is planning to turn against the church until she surprises everyone in the tomb and doesnt know Claude is distrustful of the church unless youre in the Golden Deer house. So it wouldnt make sense for Byleth to get them to ally with each other unless you change the story so that Byleth knows both dont like the church much earlier and without needing to be in a specific house.
Golden Route type endings always require specific choices. You also have a really easy way to connect them all since Jeralt's distrust of Rhea is well known. There's plenty of opportunities for communication to happen and alliances to form. The characters just don't trust each other.
This is all by design though. The devs didn't want there to be a singular best ending or they would have made one. Every route has pros & cons.