One thing to remember is that any tree that is 3000 years old has seen drought and forest fires before. Some of them were standing tall when Julius Caesar was a kid.
By the way Sequoias are named after Sequoyah, the inventor of the Cherokee writing system.
Sequoyah was probably the son of a Virginia fur trader named Nathaniel Gist. Reared by his Cherokee mother, Wuh-teh of the Paint clan, in the Tennessee country, he never learned to speak, read, or write English. He was an accomplished silversmith, painter, and warrior and served with the U.S. Army in the Creek War in 1813–14.
Sequoyah became convinced that the secret of what he considered the white people’s superior power was written language, which enabled them to accumulate and transmit more knowledge than was possible for a people dependent on memory and word of mouth. Accordingly, about 1809 he began working to develop a system of writing for the Cherokees, believing that increased knowledge would help them maintain their independence. He experimented first with pictographs and then with symbols representing the syllables of the spoken Cherokee language, adapting letters from English, Greek, and Hebrew. His daughter helped him to identify the Cherokee syllables. By 1821 he had created a system of 86 symbols, representing all the syllables of the Cherokee language.