RAM chips are not hard to produce compared to many other types of semiconductors; Intel started in the memory game and left because the margins weren't great and they were going to fold. The failure rates on these chips are actually very tolerable; you can have a very bad yield and still have a viable chip due to things like ECC.

Intel entered the memory space because they partnered with Micron. They left the memory space when Micron pulled out of the partnership.