why did Celebrimbor allow Sauron?

[Kuruharan]

What of the pride that you can play with evil, take a sip, grasp the sword, steal the bait, traverse the spider's web, and come through unscathed or unchanged? What if Celebrimbor knew, deep down, that Annatar was Sauron, or someone as powerful and as evil as Sauron, and yet thought, "I can handle this. I can allow it to go so far, and when I've had my fill, pull back."

That is an intriguing idea, and there is some evidence that might support it. I think by the time Sauron came to Eregion he had already been turned away by some of the other elves as seeming fair and feeling foul. In any event there were certainly some things to give one pause. Where exactly had this Annatar come from for one thing? Who was he really? Celebrimbor might well have had a better idea of who he was dealing with than he let on.