Originally PC only, just like TPM was originally supposed to be. It wasn't until fairly late in development that Lucasarts started discussing a PSX version of TPM.
Indiana Jones and The Infernal Machine had a PSX version planned, and indeed LEC had a team working on converting the Jones engine for use on the PSX. Then Jones had some design delays, which meant that until those delays were sorted out, the PSX conversion team was idle. So, LEC brought that team over to TPM, working like hell to cram our game onto the PSX.
TPM PSX may not look like much, but seriously it was a helluva lot of work to get it to run as well as it does. I can't say a single bad thing about the PSX team.