The AI started having this money around 1670 (it's 1771 now). It's insane. What's more is that I've completely ignored loans because nations are stockpiling cash as if they're trying to pay off the US national debt. I could do 20 wars with the Ottomans at their current stockpile and take 10K in each war and I'd still not be able to make them take a loan.
I mean they certainly have improved how they build buildings. So props to the team for working on that, but something has to be done with this money. The AI shouldn't be saving up 100K+ of money. It'll only use this money when it wants to make more money, but at this stage it can't build any more buildings. So what does it do? Spam mercs forever until you siege everything down. I don't know if this is actually intended but it sure is annoying to see an endless supply of mercs being born from money.
I mean there's other ways that the money can be spent on, subsidiaries, influence options, sending gifts to vassals, allies, threatened nations of rivals, take on foreign debt, condottieri.