When the Fed buys bills from dealers holding them, the dealers receive bank reserves. It is then up to the dealer to decide whether to reopen positions in shorter tenors like they had before, or to move into longer duration things like 5y or 10y, or risk assets. They have to choose to move out the proverbial risk curve. Some of that money does go there, but not nearly as powerfully as in QE when the Fed buys dealers' existing duration off of them, encouraging them to remain in long tenor bets. This is a crude explanation but it's why what they're doing now is not like QE. Net stimulative but different.(𝐓𝐗𝐌𝐂)