RoI isn't instant. If it takes you 20 years to build as much supply as you need then you're spending money over that time to try and get back to where you were.

And spending money on one thing means you don't have it for something else. Even if you're borrowing, you can borrow less for other things, unless you want to break your credit score, which would also hurt.

Your first paragraph is describing the effect of the loss of supply, not the investment.

I don't think Europe was anywhere close to borrowing capacity, so plenty of scope there.