Did we know all that when he and many others stated that the raid will probably fail due to storywriting issues if it didn't?
No.
Now Oda has ruined the arc on his own.
But congrats, you can celebrate the fact that "Morj and those idiots were wrong" when in fact they all had a better idea how a well written plot looks like than Oda - and I'm dead serious about that.
Actually yes. He literally did. Because he was still insisting the raid would fail as all of those happened (except Momo's speech).
This is the issue I keep bringing up. Not that Morj had the theory that the raid would fail way back before the raid, or even early on in the raid. There is nothing wrong with having a wrong theory or even a bad theory. The issue is that he won't abandon or rethink the theory as evidence piles up against it, and he and his followers keep trying to justify the theory with the assertion that it's "good writing" even as it becomes more and more ridiculous and gimmicky from a writing standpoint. It's the sunk cost fallacy.
I mean... when people first got on board with raidfail, was Luffy awakening as Joyboy part of it? Does that not effect the theory? Because it should.
As for whether or not Morj and the raidfailers had a better idea that Oda, personally I don't see it. I can see a lot of dissatisfaction around here for sure (I don't share it but I get it). But I think raidfail would have been way more unpopular.