How can the real LO and their version you obsessed over be drastically different?

It am I projecting again.

My limerent image of the LO is gone now, though I'm still limerent but not in an all-consuming manner. I think about the LO about once or twice a day and am able to shun that thought at times. I'm able to get up and leave to do my work instead of hanging out with the LO even if they call me to hang (office situation, coffee and tea breaks).

The thing I don't understand is how can the image be so opposed to what I see now. I find this person almost obnoxious now. Very immature, loud, has no worthwhile conversations, poor communication skills, not sure but maybe properly narcissistic. How could I have been consumed by this person. I actually used to think the LO was smack intelligent, had very interesting things to say, and was well-behaved. None of those things seem remotely true anymore.

Is this my mind projecting negativity on the LO as I start to see the real person? Or is the LO really what I see right now? (For ref, I had a few negative experiences with the LO which made me mentally dislike this person to an extent.)