"That the town was doomed" is a good English clause [sentence]. It cannot occur alone, because the conjunction "that" marks it as part of a clause that has higher syntactic status. It would probably occur as a sentence subject, as in "That the town was doomed was a regrettable reality," or as a direct object, as in "We saw that the town was doomed." When a clause like this is a direct object, that object is almost always the object of a verb of cognition or communication: <We know that you did it.> <She said that you did it.>
Your last sentence, "The decision resulted in that....," is not acceptable English: An English preposition, like your "in," cannot have a THAT clause as its object.