The COVID-19 pandemic caused gym closures, stay-at-home orders and a sudden surge in demand for home fitness equipment. Kettlebells became an especially visible shortage because one compact iron tool can train the whole body.
The supply chain was complex: many kettlebells were manufactured overseas, while some US retailers temporarily turned to domestic foundries to clear backlogs. A small foundry could produce only a limited number each day compared with the container-scale orders normally placed internationally.
The original article also notes seasonal casting constraints and asks buyers to plan patiently when sourcing free weights. This is a historical 2020 report, not a current inventory statement.