The math is real. In the A=1 to Z=26 cipher, corona sums to exactly 66, and the word has 6 letters, so 66 and 6 become 666. What is also documented: the cipher is English-specific. In Greek, the language Revelation was written in, the word for crown, korona, sums to 311. Hebrew has 22 letters, dozens of world alphabets give other totals. The sum works in one alphabet, chosen after the answer was known.
The story repeats across centuries with the names swapped out. Every generation's crisis gets fed into the same machine: Luther's enemies calculated the pope, the Cold War calculated Gorbachev, the birthmark counted as a mark, and 2020 calculated corona. Jesuit Ernest Hull complained in 1910 that Christendom had produced some fifty thousand beasts by this method, and offered his own name as proof of concept. It summed to 666 as well.
The interesting claim: gematria panics are a demonstration of apophenia at industrial scale. With dozens of ciphers to choose from, A=1, A=6, English Qabalah, ASCII codes, and freedom to add letter counts, word counts, or dates, any alarming word can be driven to 666. The number is not found in the word; the method is built around the number. Corona simply had the bad luck of summing to 66 while having six letters during a frightened year.
If the trick only works in English, for a plague described in Greek scripture, what exactly is being decoded, the word of God or the alphabet of the believer?