Naturally, going "him against the world' would be way too contrived in the other direction. The list of potential enemies was just that: a list of potential enemies based solely around who Marwyn speculated might have the means to do some long-range fuckery if they happened to get their hands on someone's literal soul piece. Note that he spoke of potential antagonistic motivations and agendas only in extremely general terms.You forget Cardossa,Drowned god,Leng and possible Stygoi/if it is not another name of Kadath/ as possible enemies.
But,aside from that,it is very plausible explanation of what really occured.
Brandon fucked status qquo,and everybody who do not like it would now retaliate.
It seems,that it would be Brandon vs rest of the world now.But - i like it,he need strong enemies to msde story interesting.Others alone are too small fries for that.
P.S What about possible allies? or ,at least enemy of my enemies? some powers could like his changes.
Not really actually, Luwin was right that it was a backdoor - as in, the fact he found and used it was against the design. What he did that got him burned was something else.And it seems,that Valyrian made some automated defense built into glass candles to maim anybody but them who try use it properly.
She would meet another from Asshai,Stygoi and Leng,and they made great tea party.Ariel the mermaid would join,too.Lyanna is a Disney Princess...in Westeros...oh crap.
Well, there was a positive unintended consequence of Artys' crusade, but the Valyrians never found out about it.So,Valyrians decided that gods do not exist and they must made paradise on their own,purged their kin by accident,lived in peace till Ghiscari attacked them,then they copied their way ,decide to made paradise on Earth again,blown up tkemselves.
They are kind of commies,trying to made paradise but getting hell instead.
Funny - they fucked everything trying to help.