Brock Palen the founder of ShepTech LLC, has worked in High Performance Computing (HPC) starting in 2004. In 2002 he founded MLDS-Networks.com a Joomla! and Linux consulting and hosting Provider. In 2009 he started along with Jeff Squyres RCE-cast.com a podcast focusing on HPC topics.
When I first started in HPC, we had a software title that came on physical media in a three ring binder. It covered many platforms, Solaris on Spark, AIX on Power, Linux on Power, Linux on x86, Windows on x86, Linux on x86-64, etc. Today that same package only supports Windows and Linux on x86-64.
As early as 2 years ago ARM (and Power) for HPC and data center was a major interest. So why did this happen? Looking back it appears the market wanted an competitive alternative to Intel. Maybe Intel could have avoided this situation, and they did make some decisions that didn't help, I think though it's just nature of the market.