The official truth, blasted from every media, is that they are not stranded — NASA and Boeing just want time to run some more tests.
The astronauts were supposed to do to space walks, but the space suits did not work either. Which is a problem because the space station needs some external maintenance which can only be done by people going outside in space suits. So everyone on the space station is currently trapped in a container with life support that depends on stuff outside the container, which stuff is unreachable.
The reason they want to run more tests is that most of the engines are not behaving as they are supposed to, and one of the engines has failed completely and they do not understand why. It is probably not a good idea to attempt re-entry with humans on board if you have misbehaving engines and you do not understand why they are misbehaving.
These engines have been misbehaving for years, to which Boeing has responded with denial, rather than any real attempt to understand.
Musk says that the reason is non technical management — that Boeing has managers that understand spreadsheets, but do not understand rockets. This is undoubtedly true, but evades a bigger unspeakable truth — that that these non tech managers have been firing White males and replacing them with Shaniqua, replacing real engineers with experts in race and sex grievance mongering, with people who have affirmative action degrees
Boeing was obviously taking a wildly dangerous risk by sending up a manned mission without first having a single successful unmanned flight. But neither Boeing nor NASA could notice this, because thought crime adjacent.
https://blog.reaction.la/science/starliner-astronauts-stranded-in-space/