Minecraft was memory-bound and bandwidth-bound such that it only really became possible in the late 2000's. A typical PC in 2000 would have, if generous, 128 or 256 megabytes of RAM. A typical connection, if any, would be dial up, with some ADSL and ISDN folks. Minecraft worlds, on the other hand, easily run into the gigabytes. Not to mention that all of its word of mouth came from popular Youtube videos.

You can definitely find examples of earlier voxel renderers that are also more efficient than Minecraft(e.g. Ken Silverman's VOXLAP), but memory limits and networking gaps would remain real and intractable, limiting its potential popularity.

>but memory limits and networking gaps would remain real and intractable

Those don't have much to do with Moore's law though.

Moore's law is about transistor counts and DRAM is made of transistors so it really does.