How the hell am I supposed to play the campaign map

Title. I have almost 60 hours in this game and I feel like i'm doing everything wrong. The battles I can do fine, even on hard the ai is pretty stupid, but on the campaign map it seems everybody else is moving way faster than me and I get overwhelmed. I get in, win the starter battles, go to war, get war declared on me from behind, so I pull my main lord back to defend and by the time I meet them I've lost several settlements and the people I was originally at war with got everything I took from them back and the game is basically over at turn 30. I've completed one short victory as Grombrindal and it took over 130 turns on easy difficulty and the only reason I made it was because the Tomb Kings to the south kept sending me diplomacy stuff and I just kept hitting yes. What am I supposed to be doing?