AI is unbelivebly dumb

Got radical movement as Belgium which exploded in to revolution because i was going for industrialization and was not ok of lowering power of industrialists and militarists who supported me. I first i thought it will be easy war, even though i had only 16 batalions to rebelious 22, because great britain was my best friend and trusted ally.

Picture me surprised that rebellion slowly grind me down over course of the year-long war while 120 troop sized army of britain did noting, and i got murdered watching 40 british troops in london just sitting around doing nothing, even 10 units would be enough to sway war in my favor.

Whats the point of swaying empires and making good relations if ai is stellaris level dumb and cant preform even most basic help?