From a developer perspective the two roles seem alien to each other. While it is a natural career progression, the skills aren’t necessarily the same.
Project managers tend to manage the expectation of seniors while trying to keep devs on track, QA doing their thing all the while reporting that some critical feature will certainly done by a date X.
Programme Managers tend to need way more political skills in large organizations. They are often fending the for the very existence of a project. They may be concerned with power grabs by rival teams/programme managers or trying to satisfy people who hold the purse strings which is often at odds with what customers or projects deem a priority.
In my opinion the higher up you go the more sociopathic they get so everyone is playing a large game of chess, forging relationships, writing memos, holding secret talks etc
These are entirely opinions based on little evidence other than amusing observations.
One last thought. Those write the code hold the most power, but seem not to realize this or wield it far less.