That proves that it doesn't even matter how good history in your career as a footballer and there is no guarantee if you will be a good coach. In fact, so numerous players that shifted to be a new coach were only a few that was successfully become good coach.
A general pattern. There are very few former world-class players who have become successful coaches. Most of them have had one or two stints as a coach and then never found a job as a coach again. Wayne Rooney is also very unlikely to become a successful coach. Much more successful are former players who have played in the first or second division of their country, but have never really been among the greatest. The best examples of those are Carlo Angelotti and Jurgen Klopp.
His status as a great player never guarantees that he will become a great coach. Rooney, Lampard, Paul Scholes and Maradona are a number of great players who failed to become successful coaches. Several well-known managers experienced different fates who did not gain much fame as players. Apart from the two names you mentioned above, there are several more names such as Julian Nagelsmann, Jose Mourinho and Arsene Wenger who succeeded in becoming great coaches even though they were not very well known when they were still players.
It must be admitted, it is not easy to become a great coach if you do not have a natural talent for developing team strategies.