But in the comics and movies protagonists often have falls from grace

@KingValeska ^^ I can relate

She read the literal Darkhold. What did you expect? Earlier in the MCU, a literal robot read the Darkhold and went evil.

The original script (which featured Shuma-Gorath and Nightmare as the main villains) had Wanda turning at the film’s climax rather than prior to the film’s events.

She was intended to become a key villain in a future MCU film, but when Sam Raimi and Michael Waldron came on to replace Scott Derrickson and Jade Halley Bartlett, they reworked the script so Wanda would be the villain here.

I suppose that might provide real-world context as to why Wanda being a villain felt very sudden.

The darkhold corrupted Wanda’s already tortured mind so it’s not really a plot twist imo. Add to that Wanda has been dealt so much pain and trauma throughout her life that it just became too much to bear. When you’re in that much pain and being corrupted by something that only enhances said pain, it’s hard to see the damage your doing to other people.

Not really

I mean it was known by the end of WandaVision that she was going to turn evil

And many fans did believe that she would be the main antagonist for Doctor Strange 2

I thought it was cool that she was

I mean if she wasn't, I am not really sure who would have been the main threat.

^^^I would have much preferred that version. But oh well

It was going to happened one way or another Because Wanda isn't a character that would be immune to the Darkhold like Nico or a Pure of Heart Character is. If anyone would be Corrupted by it it would have been Wanda.

I was fine with Wanda being the villan but it could've been night mare infinity Ultron or superior iron man

No! It worked perfectly!