@oytunpamuk Thats because your Xbox was found to be your primary platform.
This is determined by the highest level reached across all of your platforms. Content and Apex Coin balances will be associated with this singular account going forward, only the stats (i.e. progress) of this primary platform will be retained. The stats/progress of the other platforms will no longer be accessible.
Except for some notable exceptions, all content (including unlocked Legends and cosmetics) is available on all platforms regardless of the platform they were originally unlocked on. Exceptions include PlayStation Plus and Xbox Live Gold exclusive content, as well as the exclusive Nintendo Switch Pathfinder skin available to all Nintendo Switch users when Apex Legends launched on that platform. Exclusive platform content of this nature will remain locked to the platform in question.
There is also a small subset of content that is tied to stats, such as Achievement Badges from Apex Legend’s earlier seasons. As we are not merging stats from non-primary accounts, access to these badges through the primary account may be unavailable.
You can see more here:
https://answers.ea.com/t5/Cross-Progression/A-Quick-Guide-to-Apex-Legends-Cross-Progression/m-p/13148659#M850