Believe those are redwoods. Sequoia had little commercial value except for matchsticks.
Nope, those are definitely giant sequoia trees (Sequoiadendron giganteum). They were extensively harvested (logged) in the Sierra Nevada mountains of California.
Roughly one-third (about 34%) of the original giant sequoia acreage was logged. Some entire groves were nearly wiped out (e.g., Converse Basin became a “Big Stump” area with massive remnants). Logging was driven by demand for lumber.
But, as you wrote, the wood’s brittleness caused high waste—trees often shattered on impact, yielding as little as 50% usable timber for shingles, fence posts, grape stakes, etc.
Interestingly, Eucalyptus trees had the same problem. There were Eucalyptus plantations planted all over northern CA (the tree is native to Australia and was imported). It was the AI Boom of the time. But the wood was brittle and had little commercial value. The trees grew like weeds and area still all over the place.