Here is part of Stone's History
He was a Low level Lieutenant and his career was going no where.
He was part of Picards' Personal Guard on the Ent-D. When Riker wanted to
leave Picard when he was assimilated Stone took Picards guards and beamed
over to the Cube and brought him back. After that show of loyalty, Picard promoted him
to chief of his Personal Guard. Which did not sit well with Riker and his followers.
As Picard was promoted Stone moved up in the ranks. When Picard made Fleet
Admiral he promoted Stone and his followers to postings on the Ares. Since that was Picards'
Flag ship Stone was give the center seat for his career long loyalty to Picard.