Why would non-investment grade debt be issued at the investment-grade debt market?

Newsweek quoted Bentley University Prof. David Gulley

Ph.D., Univ of Kentucky-Lexington, 1990
M.A., University of Kentucky, 1989
B.A., Alma College, 1986

A $10 Trillion Corporate Debt Bomb Is Waiting to Explode the U.S. Economy

The Fed’s move to buy $750 billion in corporate debt, and the Main Street lending program making $600 billion in loans to small and mid-sized companies, helped indebted firms avoid bankruptcy. But it also added to the debt pile.

Aimed mostly at the investment-grade debt market, the issuance of non-investment grade debt "has skyrocketed" in the last few months, said David Gulley, professor of economics at Bentley University, Massachusetts.

"Long term, however, it’s not clear whether the now highly indebted companies will be able to survive, especially in industries like travel and leisure," he told Newsweek.

The emboldening feels contradiction to me. Why would investors who care only for investment-grade debt suddenly want non-investment grade now? Especially now in COVID19, when non-tech large cap share prices are much lower?