Fanaelialae
Legend
I disagree that it is inevitable. I certainly don't think that it's impossible, but hardly inevitable.I'm not saying that any of this is easy. It's definitely not going to be easy for a level 3ish Wizard to take over a nation. I am, however, saying that it's practically inevitable given enough time. Eventually, royals are going to notice that people with inherent magic are more respected and/or feared than those without it. The aristocracy is going to figure out that using magic, even if it's just simple, low-level spells like Arcane Lock, Alarm, and Detect Thoughts to maintain, protect, and expand their power is superior to not using magic.
It is definitely not easy for individual people, even mages, to take over the world in a life span. However, just like how money begets money and those that are born with more money are more likely to make even more money during their lifetime than those that are born poor, those born with magic or in a circumstance that grants them more access to magic/magical training are going to be more likely to get even more magic and more power in the world.
Those mage-advisors to the king are eventually going to realize within a few generations that a simple Suggestion spell or blackmailing someone with Detect Thoughts is going to allow them to control the monarchy, which will eventually allow them to overthrow/supplant the monarchy. Magocracies are inevitable unless there's something else in the setting to counter their development (like the examples I gave in the OP, like Thedas's Templars).
The only one inevitability that I see is that the aristocracy would indeed keep mages in their employ. But that's likely to be a cushy job, and most mages are going to be smart enough not to try to poop where they eat. Trying to screw over your employer isn't unlike trying to embezzle from an employer in the real world. It might work out in the short term, but I the long term they're usually caught and punished.
As an aside, suggestion isn't likely to allow you to take over a nation. Not even mass suggestion. You know that you've been affected by suggestion, plus it has to be reasonable to begin with. And that assumes the monarch isn't being protected by something like Mind Blank. All that casting suggestion on the government is likely to get you is an execution.
Look at it this way. How many world leaders in our world are hackers? Probably zero. They can pay someone to do that. Could a hacker dig up dirt on the leader and use that to blackmail them? Sure. Probably won't end well for the hacker though.
It's the same for mages. Magic presumably requires dedication to master at any serious level, not unlike hacking. Leaders have better things to do with their time than master hacking, and hackers have their own area of interest (hacking) that will generally preclude the time involved in leading a nation.
I mean, if you want all of your world's governments to be run by mages, that's fine. If you want mages to desire political power, but have some obstacles (like DA's templars) that's fine too. I just disagree that it's inevitable like you suggest.
I actually think that a magocracy would be the exception rather than the rule.