but how can golovkin get the lineal title if the guy that has it refused to fight him and is not in the division anymore, shouldn't the lineal champ be stripped if he ducks a mandatory challenger?
All he has to do is either unify all of the belts, beat Canelo or he could've asked the WBC to rank the number 2 guy, fight him and beat him.
Yes, he vacated the title. If you don't allow for that then Tommy Ryan is still the lineal middleweight champ.
It never worked that way, the Ring has added a couple of rules to avoid ducking indefinitely, but the actual lineal (something else) is just man who beat the man who beat the man, who beat a man that was appointed by a commission, who was the former man but retired, that beat the man, that beat the man.... etc. Ring and lineal have gone hand in hand for a long time because often their rankings were seen as the 10 commandments.