I actually blame apple. Essentially every one of those manufacturers wanted to replicate apples success in creating a walled garden instead of taking a different open approach. Essentially lack of visionary thinking.
As you said Samsung is terrible at DevRel, but Tizen OS itself is now pretty good. Tizen's survival in medium term is assured since it ships in Samsung TVs.
On the other hand, I am not sure even stellar DevRel would have saved Tizen. Yes, Sun was terrible with OpenSolaris, but wasn't Joyent stellar with SmartOS (which is the same codebase)? That didn't make SmartOS very successful.
Keep in mind that HP did the same with webOS, Sun with OpenSolaris etc. So, its not exclusive to Samsung, but rather big enterprise not understanding the outside world.