How can they "wash away" the caffeine from Nescafe Gold to produce that "de-caf" version? I buy and drink Nescafe Gold all the time. I also buy the smaller "caffeine-free" version of the same product. It tastes very differently, which makes me assume that the caffeine does have a lot of taste.

However, maybe it's not simply due to the lack of caffeine? Maybe the process with which they "de-caf" the original product (something about "washing it away", if I recall correctly from what I read/heard somewhere at some point) also removes other ingredients?

How can they possibly "wash away" just the caffeine from instant coffee like that? 

Unless the truth is that the entire products are "built" from the ground up, separately for the caffeine-including and caffeine-less products, and the latter is not "based on" the former at all? 

Even if so, they still have to "wash away" the caffeine from the raw coffee, which puts us back on square one...
In general they use different types of solvents and methods to wash away the caffeine (or at least a great percentage of it) from the coffee beans , you can find more information here : https://www.todayifoundout.com/index.php/2011/04/how-decaffeinated-coffee-is-made/