I've had the same happen since the beginning of posting on steemit years ago. I have had posts I was really proud of that got nothing. Then I'd post something casually with a lot less effort and it might do really well.

I just stop trying to predict or post based upon such things. I just write what I am inspired to write. Most of the time it is lengthy. Sometimes it is not.

I don't even attempt to guess at how well they will be voted on.