The same reason for all the rare diseases returning of course
Multibacillary leprosy unmasked by COVID-19 vaccination
'The patient's symptoms and clinical and histologic findings were consistent with multibacillary leprosy. Given the temporal relationship with COVID-19 vaccination 10 to 15 days previously, his reaction was likely unmasked by the COVID-19 vaccine.'
https://pmc.ncbi.nlm.nih.gov/articles/PMC8610845/