Originally MIPS (or DLX) was the dominant architecture used for teaching computer architecture because the standard Computer Architecture textbook (by one of the main designers of MIPS, David Patterson [1] along with John L. Hennessy [2]) was used in most universities [3]. These two authors were basically the university-lead designers of the RISC philosophy. Patterson's team designed the RISC-I and RISC-II processors (Berkeley RISC [4]). Hennessy and his team designed the MIPS processors (Stanford MIPS [5]). This culmination eventually begot the RISC-V. So yeah, the RISC-V is now the dominant architecture used for teaching computer architecture as they now use RISC-V to teach computer architecture with their latest book edition [6]. Also for more information on that, read [7].

[1] https://en.wikipedia.org/wiki/David_Patterson_(computer_scie...

[2] https://en.wikipedia.org/wiki/John_L._Hennessy

[3] https://www.amazon.com/Computer-Architecture-Quantitative-Jo...

[4] https://en.wikipedia.org/wiki/Berkeley_RISC

[5] https://en.wikipedia.org/wiki/Stanford_MIPS

[6] https://www.amazon.com/Computer-Organization-Design-RISC-V-A...

[7] https://en.wikipedia.org/wiki/RISC-V#History