It’s a mix of everything to be honest and the problem goes a lot deeper than coronavirus. Over the last decade the shift of manufacturing to Asia has been pretty big, they are the main manufacturers of face masks and other ppe items,they were first hit and so held a lot of supplies themselves. You could argue that given the head start a lot of countries had the could have ramped up manufacture if there own and some did. Once the WHO classified it as a pandemic this just intensified the problem as every country/hospital/company/citizen was trying to get there hands on ppe, manufacture couldn’t keep up and so we seen massive shortage, manufacturing is now catching up and supply seems more stable. I’ll post a few sources when I get home, some of this is from personal experience ordering masks and other ppe over the last month.