I wonder how we'll pay for it
Someday, somehow, all this will have to be paid for. It's not to early to suggest that either taxes will rise or spending will be cut. Given how hard it is to cut spending, my guess is that taxes will rise after a few years when markets start to get uncomfortable with the towering and growing pile of debt.
Also likely is that the Fed monetizes the debt. That is, "QE-Infinity". QE stands for "quantitative easing" which is code for buying debt and pushing cash into the financial system. When the Fed does that ad-infinitum, they are printing money in a literal sense. The intended merit of such an approach is that in a deflationary environment, we need inflation which money printing is supposed to bring about. Remember, most debts are fixed. A mortgage refinanced today does not see its principal adjust for inflation. In 10 years, the borrower will be paying back that same 2020 debt with 2030 inflated dollars. It is the most painless way to reduce debt burdens.
We should consider that inflation is likely to rise in coming years. Probably not for a while, but in the 2-5 year time horizon. That may require finding inflationary hedge investments in the next couple years. Something to ponder.