The 25-year-old moved to Leeds in January from Club Brugge penning a four-year deal with the club but failed to make a major impact at Elland Road making just seven appearances.
United manager Paul Heckingbottom replaced De Bock with academy product Tom Pearce before he was sacked in June with the Belgian told he could leave the club.
De Bock though says he enjoyed pre-season under new boss Marcelo Bielsa after being handed a chance to prove himself but felt it was necessary to explore first-team chances elsewhere after the arrival of Barry Douglas.
"The coach [Paul Heckingbottom] wanted me to leave, but was fired in June," De Bock told HLN.
"Under Bielsa I did not have to leave last month, but after the arrival of a new left-back I thought it better to go.
"Bielsa has a lot of appeal, it is as if he invented football. I learned a lot from his vision and philosophy. Leeds was an adventure in itself and I feel like I'm coming back [to Belgium] a bit more mature."
De Bock also revealed that a return to his home country wasn't the only option he had this summer but it was the one that felt right.
"There were several possibilities, but KV Oostende is just what I was looking for", De Bock continued.
"I almost sat on the plane to Jerusalem. Beitar was interested. Playing in Israel would have been an adventure, but now I am happy to be back in Belgium together with my family. "