Marcus Aurelius was both an Imperial King, as well as a Philosopher.....though he was not, a Philosopher King-(from the Platonic perspective).
One would think that because Marcus Aurelius had the skill of a Politician and the wisdom of a Philosopher, that he would have been History's First Philosopher King. However, one should not be so linear or logical in analyzing the life and writings of Marcus Aurelius. The historical personage of Marcus Aurelius, like many other significant figures of the past, was more complex and nuanced.
Marcus Aurelius was the Emperor of Rome during the 100's AD/CE, which incidentally, was the height of the Pax Romana-(or "Roman Peace"). The Roman Empire, in terms of territory, had reached its zenith under the imperial reigns of Hadrian and Marcus Aurelius.
However, unlike Hadrian and nearly every other Roman Emperor before or since his time, Marcus Aurelius was an actual Philosopher, who wrote rather prolifically on Stoicism. While he was not the originator of Stoical Philosophy, he certainly refined, advanced and spread its teachings to a much wider audience.....the Roman Empire.
But, one should remember that Marcus Aurelius ruled Rome and its Empire with an "iron fist". He was no fan of the growing Christian community who were persecuted under his rule-(The Coliseum was alive and well during his time as Emperor). And, Roman Law had not really changed much since the days of Augustus. So when looking at Marcus Aurelius' political bio, he was not exactly the idealized Platonic Philosopher King.
Essentially, Marcus Aurelius, was a Roman King and Emperor, who also had a second identity as a Philosopher....though his two identities, were irreconcilable.