It's strange to call this an "alternative explanation", since it's the one that expert infectious disease researchers, nearly without exception, are pointing to.
The (let's face it, silly) notion that masks and distancing suppressed all respiratory pathogens except one is a theory with very little traction, and which will almost certainly not stand up to serious scrutiny.
The (let's face it, silly) notion that masks and distancing suppressed all respiratory pathogens except one is a theory with very little traction, and which will almost certainly not stand up to serious scrutiny.