The AI will break their country with thousands of ducats of loans and mercenary armies to try and stop the player, while leaving their lands undefended and slowly sieged down by another war.
This is not smart unless the only goal of the AI is to stop the player.
The AI will take massive loans to fight any war. Playing the game you will eventually see a big red X in your CtA screen due to allies on one side or another having massive loans, all without player involvement. Have seen it less often in 1.18, sample size too small to be sure. This is not smart, but I haven't seen any anti-player bias.
For those trying to prove that the ai is behaving correctly please relate the time when you are in a war with a big power and another big power attacks your most powerfull ally but the ai doesnt care and literally lends you all their troops even though in the end they will be 50 % annexed. The ai never does that for the player but against the player? It seems like this is the norm from now on.
I think you got a bit mixed up there. You are describing precisely the fall of Hungary in your game: Hungary (you) are in a war against the Ottos, France attacks Liege with automatic co-belligerent on Austria (your powerful ally) and Austria definitely does NOT lend you all their troops, instead fighting for their own interests (safeguarding the HRE).
...I see in your screenshot that, actually, Hungary's army is sitting there defending itself and not helping against you? So if you were Austria in this scenario, AI Hungary is not literally lending you all their troops, allowing themselves to be 50% annexed?