Hey there powerViking, I understand your Question, maybe because I´m a Viking to (sweden)

The answer is: First of all it shuts you down, meaning that once you end the cycle you wont have any test in your body and therefore cortsol will be the dominant hormone and that is catabolic and will make your muscle dispear

. Second: D-Bol is easy converted in to estrogen in your body witch will couse weater retention, and once the estrogen goes away you will piss out all the exesive water and lose weight fast.
You are simply in a very catabolic state when you stop taking the D-bol and that will eat up most of your gains.