Sauron's Great Miscalculation

[Inziladun]

Originally Posted by Feanor of Helcaraxe

I don't think it was, Sauron gained his most powerful servants (the Nazgul) with the use of The One Ring, this helped in the crippling of Arnor. You also fail to take into account that The One Ring greatly enhanced Saurons power which was very important given how Sauron's enemies were much more powerful at the time. His fortification of Mordor after his return to Mordor after the war of the last alliance was made easier given that the foundations of Barad dur still existed thanks to the ring.

Hello, friend. Welcome to the Downs!

You're quite correct in your assessment of the Ring's positive effects for Sauron.
However, the initial premise here was that Sauron was foolish because of his motive for making the One Ring. Its purpose was to help him control the Elves. The subsequent benefits to him were not, as far as can be seen, in his thoughts when he fashioned it.
So,even though the Ring obviously did aid him later, it can still be said he was indeed a 'wise fool' whose plan failed from the start, and eventually led to his downfall.