Because the government is a terrible market participant. It has infinite money, they suffer no consequences, and ideologues come up every so often and let their agendas take over any economic objective the program had in mind.
This is happening now more than ever with the Democrats seemingly deciding that the US Fed has the additional mandate of fighting systemic racism.
The Fed board is appointed by the President and approved by the Senate. The current chairman was appointed by Trump. The article doesn't even mention racism so I guess this is probably a throwaway culture war post but I have a hard time seeing how this of all things could be pinned on the Democrats. If anything it's the anti-public-health Republicans who let the pandemic get out of control and lead to a Fed buying spree.
This is happening now more than ever with the Democrats seemingly deciding that the US Fed has the additional mandate of fighting systemic racism.