they're more anecdotal experiments than something usable
Wrong. Microsoft explicitly set out multi-architecture support as a design goal for NT. MIPS was the original reference architecture for NT. Microsoft even designed their own MIPS based systems to do it (called 'Jazz'). There was a significant market for the Alpha port, especially in the database arena, and it was officially supported through Windows 2000. They were completely usable, production systems sold in large numbers.
In the end, the market didn't buy into the vision. The ISVs didn't want to support 3+ different archs. Intel didn't like competition. The history is all pretty well documented should one take the time to learn it.
Except they did, though apparently you missed it. MIPS was the original port. Alpha was supported from NT 3.1 through Windows 2000, and only died because DEC abandoned the Alpha, not that Microsoft abandon Alpha (it was important to their 64-bit strategy). Itanium was supported from Windows 2003 to 2008R2. Support for Itanium only ended at the beginning of this year, once again because the manufacturer abandoned the chip.
I'm sure you can redefine "achieve" to exclude almost 17 years of support (for Itanium), if you're that committed to being right. Heck, x86-64 support has "only" been around for 20 years or so. Doesn't make it right.
Wrong. Microsoft explicitly set out multi-architecture support as a design goal for NT. MIPS was the original reference architecture for NT. Microsoft even designed their own MIPS based systems to do it (called 'Jazz'). There was a significant market for the Alpha port, especially in the database arena, and it was officially supported through Windows 2000. They were completely usable, production systems sold in large numbers.
In the end, the market didn't buy into the vision. The ISVs didn't want to support 3+ different archs. Intel didn't like competition. The history is all pretty well documented should one take the time to learn it.