Answer
I have good news, and I have not-so-good news. The good news is that you CAN re-stain your cabinets. The not-so-good news is that you aren’t going to get away with a light sanding. You will need to strip the finish to remove any hint of a sealer coat, then you will need to lightly sand to prepare the wood to receive the stain. Then you can stain with a darker stain, (not a lighter stain) and finally apply the finish coat.
A wood conditioner does not work like shampoo or fabric softener. It is actually a sealer to “level” the wood’s ability to absorb stain. It is used with soft woods that absorb stains in the spring growth (the white rings) better than in the summer growth (the brown rings) which looks irregular. It is also used on hardwoods such as Birch that “blotch” when stained.
This time, try your stain on the inside of a little-used cabinet, such as above the range hood, to verify the color.