I don't want to sound crazy but this kinda of scenario happens on my games without mods (on console, actually)
Currently playing (deity) with Cleo and having Chandra as a neighbor together with Robert and things are spicing up now on end-Medieval early-Renaissance with me and Chandra ready for a [formal or joint w/ Bruce against Chandra] war (I want two cities of India) while at my south border Jadwiga keeps trying to convert my cities while I'm using a couple of apostles to hold out (my religion gives me money so is paramount to protect it). I asked promises for both of them and they declined and now I also have a Holy War Casus Belli if needed later.
The military numbers are high for everybody here. Robert was with war against Jad and went to capture Wrakow only to lose it when the Era changed and he got a dark age. Chandra went to capture Armagh early Medieval since he couldn't expand over me on early game (oh boy, but he built a army to try, don't know why changed his mind) and reinforce his walls since he denounced me.
Sometimes I feel that we as players need to do all those "rituals", or "acting" on those rules (promises, denounces, Casus bellis) so the AI can responde properly and even doing that you need to consider careful how much you will take on a war (or if you will take at all) to not disrupt diplomacy with other players. It's a interesting balance, but I believe some players want more action throughout the whole game.
On the aforementioned play, I'm allied with Robert (he is bottom low on score) and friendly with Ambiorix on the other continent. Don't want to commit with him yet bc he is in bad terms with Mvemba and Sendeok and I want to be able to trade with all of them until I see a clear opportunity to commit with someone there. I also try to influence on their results based on gossip (someone is at war, so let's see if they need luxury or strategic resources for wage war). Don't know if this helps, but it really makes thing immersive.