It is more than IBM used to be a big name in areas where hackers would be expected to be. They have left all those behind though. there are lots of other companies that none of us would recognize that are big, but IBM is a name that we all know as once somewhat important who now are not.
Right. If you are in the HN bubble, then 30 years ago IBM was a big name in computing as the inventor of the PC, OS/2, maker of a great keyboard, and a bunch of weird systems we never touched. They sold their PC and keyboard businesses, and let OS/2 die. We think some of those weird systems still exist, but those never were very relevant unless you had to work on them.
HN users are trendy. If you didn't grow up in the 1990s or before though you may not remember just how picked on this type of crowd was. Now while we are never exactly the "in" crowd, we are respected, being a "nerd" or "geek" is now an acceptable thing. We have come a long way and that is enough trendy enough for us.