Dan Tanguay, one of the designers of Crash Bandicoot: N. Sane Trilogy says that this game is a remastering done "practically from scratch" but that they had access to the source code of the originals.
For the remastering of this game was missing much source code as well as other support materials used for the original game. The graphics engine in this game was only used for this trio of video games and was not used for any other.
This graphic engine was not used beyond the playstation 1 which complicates things even more.
Video author #youtube Tealgamemaster
