Let's look at the facts:
1. Kaido has the Strongest army in the World. Big Mom doesn't at all, that's why she was hell bent on getting the marriage with the Giant's Race. Giant's who are consistently hyped by Oda.
2. The story(One Piece) doesn't make that clear, it's just something spade said in the Ace novel, something that should be taken with salt considering Spade also implied Shanks was the weakest emperor, which by Kaido's logic, isn't true.
3. King is a monster. His feats are rivaling his captain. We also know Kaido felt extremely comfortable going to Marineford and Whitebeard with King alone by his side. That alone speaks to the absurd strength of King.
4. Yes, Kaido's army would wash Big Mom's. Why? Because Big Mom barely looks for strength in her crew, she looks for races. Kaido is looking for strength. The difference in their crew would and should be noticeable, it's simple math.
5. No one said it would be easy-easy for King to dispose of them, but they have nothing against him, so it would be easy. Their strongest commander's hax and awakening is easily dismantled by King's speed and fire alone. Smoothie and Cracker are no challenge. Another thing, the sweet commanders are not relative at all, their stats don't compete. Katakuri's speed is his strongest suit, and King still has the advantage there.
6. Cracker can probably cut Kaido, or maybe even Smoothie, or Kat. But we aren't talking about Kaido, we are talking about King, the guy with the defense that took a high-tier move from Zoro without a sweat. Hurting Kaido is easy as long as you have the technique, King can easily withstand techniques that hurt Kaido.
And to add to that, having the technique to hurt Kaido doesn't mean you have the AP to do competent damage. +1000 G4 Luffy still could only deal shallow damage, and he's stronger than Kat. 1000 or 1010 Luffy aren't doing anything to King. It's not hard to see why King dog walks dogtooth and his siblings. It's really not.
