Because of the way bonds are priced, by buying so many, the Federal Reserve effectively lowered the return on them, which incentivizes other investors to lend to riskier entities— like small and midsize companies— in order to get a decent return.
Gracias a la cotización de los bonos, al comprar tantos, la Reserva Federal pudo bajar el retorno, lo que incentivó a otros inversores a comprar bonos de entidades menos seguras como PyMEs, para tener una mayor ganancia.