Inflation isn't just a fiscal (even though Biden failed on the fiscal side as well) or monetary phenomena, it's psychological - i.e. expectations about future prices.
Because the Biden administration was characteristically incompetent (Remember Treasury Secretary doing interviews saying that inflation was just a short-term blip and not persistent?) inflation started to get out of control. Once that happened, 30+ years of low inflation expectations went out the window. Market psychology changed, and because people now expected prices to rise, they weren't as resistant to individual price changes. This gave producers (along with legit covid supply side issues) breathing room to increase prices.
Because the Biden administration was characteristically incompetent (Remember Treasury Secretary doing interviews saying that inflation was just a short-term blip and not persistent?) inflation started to get out of control. Once that happened, 30+ years of low inflation expectations went out the window. Market psychology changed, and because people now expected prices to rise, they weren't as resistant to individual price changes. This gave producers (along with legit covid supply side issues) breathing room to increase prices.