On Communication, it is habitual in EU jargon to capitalise official EU documents and institutions.

The sentence with the 'mistake' isn't the prettiest, but I don't know if it contains grammatical errors. I'd reformulate it as 'It is a fundamental mistake to assume that profitability will automatically attract investors to a project'.

Though I do not know what the precise meaning of the sentence should be.

Perhaps it is better to write 'It is a fundamental mistake to assume that profitability should drive infrastructure investments'.