It doesn't have to be 20lbs.
A fully beefed up Razer Blade with GTX 2080 weights 4.7lbs vs a much less powerful Macbook Pro's 4lbs.
Thickness of 0.7" vs 0.61"
That doesn't have a mechanical keyboard, which will add quite a bit of weight and thickness (which adds more weight).
The one laptop that ACTUALLY has a mechnical keyboard, the MSI GT83, weighs 13lbs not counting the 2 (!!) 330w power supplies. Shipping weight is 24 lbs.
Honestly, that machine is more a "luggable" than a laptop, in the grand tradition that includes Kaypro CP/M and Commodore SX-64 luggables with built-in CRTs.
