What is deranking?
Deranking means a cs go player purposely losing the game in order to get deranked ( low csgo rank ),

There are a lot of reasons to derank some might be

a few cs go gamers desires lower ranked cs go account to play with buddies
some gamers need an account with lower ranks csgo account so that they can play on without much stress
or even they want to try some crazy strats!