Myocarditis and Pericarditis NOT associated with COVID-19

These two studies show the increase in myocarditis and pericarditis are not linked to COVID-19, the virus. This means something else has to be causing it. What could it be?

https://pubmed.ncbi.nlm.nih.gov/35456309/

https://www.sciencedirect.com/science/article/pii/S1054880720301046