Possibly the case that when you were eating carbs, you were putting away 3500 calories a day, and that dropped to 3000 calories a day when it was just meat? I know that just a casual stroll through the mall on a refeed day for me, I have zero difficulty putting away 6000+ calories - refined carbs are shockingly calorically dense.

Also - for some time on a Keto Diet, you are going to be dropping a ton of water - so the scale will be dropping like a rock, regardless of what your actual body weight is doing. Getting a DexaScan, or whatever lean/fat body mass assessment you prefer to see what's really going on.