It's not just a multiplication instruction. The CPU is equipped with a fixed-point coprocessor to accelerate the most common computations in 3D games, the geometry transformation engine [1], capable of carrying them out much faster than the CPU alone could. For instance, the GTE can apply a transformation matrix to three vertices and project them in 23 cycles, while the CPU's own multiplier takes up to 13 cycles for a single multiplication and 36 (!) for a division. Combined with a few other "tricks" such as a DMA unit capable of parsing linked lists (which lets the CPU bucket sort polygons on the fly rather than having to emit them back-to-front in the first place), it allowed games to push a decent number of polygons (typically around 1-3k per frame) despite the somewhat subpar performance of the cache-less MIPS R3000 derivative Sony chose.

If you have some basic familiarity with C, you can see both the GTE and the Z bucket sorting of GPU commands in action in the cube example I linked in the parent comment.

[1]: https://psx-spx.consoledev.net/geometrytransformationengineg...