As someone who programmed drivers for nt, it’s not, the reason it’s easier is because they started later.
Xbox is a mature x86 windows platform, vs ps1 which is an embedded mips system.
They started with their windows directx stack and just kept with it, while ps did a random walk all over the place.
Msft also had really boring hardware, like, they started with a crappy pc, then made a crappy ppc pc, then went back to a crappy pc. The software was simplistic, while Sony made really interesting hardware designs, that turned out to be hard to program, till the ps4 when they just gave up.
Msft traditionally isn’t very good at operating systems, they’ve just had infinite resources and infinite monkeys for 40+ years, and they’ve been stubborn enough to make it work somehow.