cross progression caused me to lose all of my heirlooms and progress

i had an xbox account with a bunch of progress and a bunch of heirlooms. i switched to pc and tried to do the cross progression on my steam account i logged in and then linked my steam account to just to literally lose evrything ive ever owned even my heirlooms. i cant unlink my accounts until september. why is this even a thing? ive spent so much money and played this game for at least 6 years now and now everything is gone...