My initial impression of Pathfinder was that it was meant as the PnP home for everyone who kind of hated the Eberron game setting and 4E's attempt to make D&D more steampunk WW1, more video gamey or board/card gamey, and generally more MMO-like in the late aughts. Exemplified by like the D&D Insider plan and then D&DO which put Eberron rather than the Realms as it's main setting up front.
But then D&D did a straight u-turn, like a really hard course correct, abandoning just about everything they tried to do with 4E. Such that now I guess Pathfinder seems like the ruleset with the more video gamey bent, and the more steampunkish vibe by comparison, since the pendulum swung so hard in the other direction with 5E? lol
For the rules Pathfinder 1E is just D&D prior to the 4th edition divide with some minor adjustments here and there. Golarion is pretty much a Faerun knock off, with a little name substitution, that tried to keep the generic flavor of the Realms under a 3rd edition theme ruleset, but when D&D was way too busy trying to master the Internet and be all new wave hehe.
Doubtless the suits at Wizards were probably pissed that Blizzard was enjoying so much success with WOW, and wondering why they weren't making the big cheese with D&D? Like Renton vs Irvine, who's going to cash in on these orcs! But 4e was like roundly rejected when it launched. Not to knock Ebberon too hard, it's not that the setting was bad, more how it was presented. Along with all the other big changes that came too fast and were originating with the designers desires to make it "new" in a top down sort of way, rather building on or codifying what players were already doing, which is how the prior editions AD&D, 2e, 3e and 3.5 all worked.
A few designers had to fall on their swords I guess, but it was a big group effort that collectively missed the mark and lost too much money and too much marketshare to ignore. Instead of making up lost ground, they just ceaded even more of it, as many players switched to Pathfinder at the time. Pathfinder was like comfort food compared to the food truck fusion fair D&D was trying to serve up before 2010. Now the situation is rather different. Mearls esp probably learned a lot from what didn't work in 4e when they were building out the next ed, because the popularity and general vibe of 5e has brought many people home again in the intervening period.
I'd still take the Realms over Golarion no contest, since the Forgotten Realms is the 'original' knock-off fantasy game setting lol, it's just hard to compete on the lore front there. I suppose D&D is giving us Gith these days, and soon Faeries and Rabbitpeople and other things like that to distinguish itself from Pathfinder in more ways. Though Golarion has been getting more interesting as its been fleshed out more too. I sometimes wonder, if 4e didn't try to change both the rules and the principle setting at the same go, or if Eberron had been introduced without an attendant massive rules overhaul, if either might have been received better? But what happened happened I guess, and now we got a split. I think there is some merit to the idea that PnP and video games might benefit from having slightly different core systems more adapted to suite the medium, but I think they kind of learned the lesson that making PnP more videogame like was rather less popular than they imagined.
