$4t was printed to bail out the banks. What is stopping more money from being printed this time, in the form of economic stimulus?
In a related issue, there's a theory making its circles in both right and left camps that if inflation is sub-par for a while, say below 2%, then printing more money won't cause problems.
Why inflation is lower than expected is an economic puzzle. But printing money to avoid paying debt may create new economic puzzles. If they try it, try it gradually please.
(The ideal annual inflation rate tends to be around 2.0% to 2.3%, based on historical record. This is in aggregate. Highs or lows tend to affect different people differently.)