I have no idea what happened but from an economic standpoint (and as a player of numerous strategy games), having a large amount of infrastructure would be counterproductive. This is due to some quick calculations I ran, and the least economical way of powering all 20k infrastructure would be to build 80 windmills. Now with 20k, you get 400 improvement slots (20,000 รท 50 = 400), and of those 400 slots only 195 would be used by getting max amount of everything that can be made. Also buying more infra is a compound investment, costing more as you buy more (which is odd, but I guess it's to prevent megacities being rapidly build). Also you need many resources to build most of these improvements so more expenses.
Yeah I don't think 20k infrastructure is worth it.