Capital isn't injected, it's hoarded.

The rich are already doing fine. They're doing better than they have since 1920. As a class, they have so much money that they're able to do stock buybacks because investing it doesn't give moneygasm-style returns. We're nearing the point where they can Scrooge McDuck-style swimming pools full of cash.

The problem with the current economy is very much not that the wealthy don't have enough free capital. Quite the opposite, really.

The problem is that they have so much free capital because they're addicted to non-productive methods growing their wealth.