He fooled everybody. Like in
the old days in
Numenor. Or when he helped the
elves with the rings and they didn't get his schemes. The old joker:
Sauron deliberately spread the belief that
the One Ring could only be destroyed in the fires of Mount Doom. He influenced
Saruman with the
palantir and Saruman told it
Gandalf and
Elrond. Everybody took it for granted. But nobody was ever able to proof it, of course. Why should it be destroyed "now" in Mount Doom, just because it was forged there thousand of years ago? There is no cause and effect. Sauron knew his enemies wanted to be “good” and would refuse to use
the Ring themselves. So if they found it, that was his trap. Otherwise he would have destroyed this big volcano next to his front garden. No other reason to leave it unguarded and still active.
Gandalf killing thè only other Mair, thé
Balrog , that was unexpected but rather helpful for Sauron.
That's why he left the Sammath Naur unguarded and kept Mount Doom active, turning it into a trap. He build his tower close by to be there to collect it. When the Ring was cast into the fire, the visible collapse of
Barad-dûr and the destruction of the
Nazgûl actually occurred — but this was an outcome Sauron had anticipated or triggered.
Just a cheap slideshow, like a magician. "Look at my right hand" while the important stuff happens somewhere else.
Tolkien wrote that the "Ring is gone". Sauron was able to collect it easily when his celebrating enemies went home.
With the Ring, it's so easy to build a new tower, more suitable to a nicer appearance and create thousands of
Orcs in a minute. The only thing his enemies see is a fleeting shadow. And with their belief and all the chaos of course they think it's his remains.
So the good guys, His enemies, believing him finally defeated, withdrew and celebrated. Sauron then recovered the Ring (which had not been truly unmade) and, with its power restored, could rebuild his strength.
Just biding his time until Gandalf left for
Valinor and
Aragorn is too old and hey, surely the palantir is helpful in the future.
The entire quest rested on an untested assumption. This version alone, this reading resolves the major strategic inconsistencies without requiring Sauron to act irrationally. Why should Sauron, clever guy he is, make such a huge mistake and leave the volcano unguarded? Why should Tolkien create such a logic hole, perfectionist that he
is? Who will ever know what's written in the letters that weren't published after his death. And don't forget a similar case, Mark Twain's dark tale "Stranger" which was only published after his death. That was Tolkiens greatest trick, greatest invention, greatest secret. Genius!