The key word in my comment is ‘early’. You’re right about architectures today but that explicitly wasn’t what I was talking about. Caches we’re important in the IBM 801 but your orher points don’t apply to early RISC designs.
I actually cited an example of a major CISC design that basically failed because it was so buggy.
The early microprocessors all had hard coded microcode - Intel only had upgradeable microcode with P6 in the mid 1990s.
I didn't say that it was the reason - there were many reasons - but that it was one factor. It was absolutely the case that original RISC designs were simpler to design and that helped them to get traction.
Edit - just to add that caches enabled RISC to get decent performance but they were not by themselves a reason for choosing RISC over CISC.
1990? No system without soft microcode? That's a very restricted definition of system for the field of computing in 1990.
Intel 8086 was introduced in 1978, with hardcoded microcode. Intel didn’t introduce microcode patching support until the Pentium Pro in 1995.