You are confusing medium intelligence with high intelligence I fear.

Truly intelligent people won't be getting into doom spirals and self-sabotage. They will - obviously - use their superior intelligence to avoid that situation (or mitigate it before it becomes an issue), but the merely middling folks get trapped by it and cannot work their way out of it because they're just not intelligent enough to realise it is happening and/or work out how to stop it.

Good luck.