Because Liverpool were the equivalent of Derby back then.
Indeed. Apart from the ground of course! This from Wikipedia.........
Shankly became the manager of Liverpool in December 1959.
In 1959, Liverpool was a club in the bottom half of the old Second Division, with a crumbling stadium, poor training facilities, a large and poor quality playing staff and had been knocked out of the FA Cup earlier that year to non-league Worcester City. The only quality was in the backroom staff, with Joe Fagan and Reuben Bennett, added to by the recently retired footballer Bob Paisley, whom Shankly admired.
The training ground at Melwood was in a terrible state, overgrown and with only one mains water tap. Shankly turned this into a strength, by getting the players to arrive instead at Anfield, and then bus them over to Melwood - this created team camaraderie. At Melwood Shankly introduced fitness training including diet assessment, and skills training including using an artificial goal painted on a convenient wall, split into eight sections which he would demand the players hit each time. For playing practice, Shankly introduced five-a-side games that so defined his football thinking - pass and move, keep it simple, a creed taken from the daily matches played by the miners of Glenbuck. After training, the team would all bus back to Anfield together to shower, change and eat a communal meal. This way Shankly ensured all his players had warmed down correctly and he would keep his players free from injury. As a result, in the 1965-1966 season Liverpool finished as champions using just 14 players and two of those only played a handful of games.