That may have a lot to do with the fact that the DB2 as implemented on the AS/400 (now iSeries) is extremely easy to use and, unlike Oracle and others, NO DBA is needed.
BTW, your link doesn't work for me - is it okay??
As to market share, please use current stats. I used a 1996 article to show simply that 64 bit computing (real, not "faked") has been around for quite a while - I believe the first as/400's with the 64 bit rsc rolled out in 94 or 95 (at the time that M$ was rolling out it's flagship 32 bit system).
You said that right, There are only two of us managing 4 production iSeries 400 machines with 20,000 users on them (at the same time). With DB2 we do not have a database administrator, just a few applications people. On the iSeries 400 you don't worry about the database just the application. And its all 64 bit.
And yes we drive front end GUI applications on the web, of course the end-user does not know they are on the iSeries.
Other operating systems crash 4 or five times a year but OS/400 on the iSeries is rock solid. has not crashed in years.