Coast Redwoods don't often reproduce from seed. Instead, they sprout from a (live) stump or from the base, trunk, or roots near the trunk of a living tree.
And yes, this commonly causes a "fairy" ring of trees to grow around the base of a mama-tree stump.
And then of course the same thing can occur for trees in that ring. And on and on. You don't notice this neat recursive pattern because some trees in a ring don't "make it", while others do, and as it's happening all over the place the result, except for single fairy rings, is obscured.
All such trees are genetically clones - same genes. And they join at the roots (and sometimes at the trunks). (And they share more, by way of shared mycorrhizal fungi.)
In some ways, such a group of clones could be thought of as a single individual.
Why do they have so many tiny cones with so many seeds, if they don't use them? They use them after a fire or a flood. (Stumps can also sprout then, if not completely killed.)
These critters are nearly impervious to fungi, insects, fire, floods,... A felled redwood tree trunk can lie on the ground hundreds of years without rotting. Then another tree falls across that one. And on and on, over the centuries... And bushes and trees (including redwoods, related or not) grow on top of felled trees. The "floor" of a primeval redwood forest can be lumpy, with deep "holes". You might think you're walking on the ground (whatever that might be) when you're walking along tree trunks.
Strange beasts. Almost like filter-feeders in the sea, their leaves (sprays of needles) are fine feathery filters that grab the cold Pacific-blown fog like a sponge. It's really about fog as much as it's about rain.