One factor that I think has helped a lot is Kickstarter / crowdfunding, which helps mitigate the costs of a first production run.
Another factor is DRM in video games -- why spend 4x$60 on four licenses for a multiplayer video game and hundreds more on hardware, when you could just spend $50 on a board game and have it support four to six people?
Pathfinder in particular is booming because all of its game content is literally open source... inherited from the D&D 3.5 "Open Game License".
There are plenty of online databases and apps that get you the entire rulesets of Pathfinder. Paizo's official one is here: http://paizo.com/pathfinderRPG/prd/
You can literally play all of Pathfinder (including all of their optional rules) without spending a single dollar. But the books, adventure paths, and art is so lovely that the GMs and hardcore players are willing to buy them up anyway.
As someone who has been playing boardgames for 20+ years and computer games for even longer I can tell you that neither Kickstarter nor DRM are relevant factors here. In fact, both came much later than these trends started.
Broadly speaking, tabletop games are divided into what are called Euro games and Ameritrash [1]. Euro games have less player-conflict and (often but not always) less luck.
Euro games either originated in or were popularized in Germany and the beginning of that trend is really Settlers of Catan and (later) Carcasonne. Both of these games were and are big but for the more "serious" Euro games, the trend really took off with Puerto Rico, which came out in 2002. Since Puerto Rico there has been an absolute explosion of games.
In the 90s we might've had 10-20 games to choose from? Now, hundreds.
Every few years there tended to be a standout game which would propel the industry in some way, often evidenced by the many knockoffs. Agricola (2007), Race for the Galaxy (2007; although it was largely a rethemed San Juan (2004), which itself was inspired by Puerto Rico) which led to Dominion (2008+), Terra Mystica (2013), etc.
Kickstarter is really feeding off this success not the other way around.
As for DRM (including copy protection), this has been a thing most of the life of computer gaming. Now is really no different other than DRM of the last 10+ years has moved towards always-on Internet connections or, worse, turning single player games into games that can only save online (eg the SimCity V fiasco).
My experience with LAN gaming was it was one of two types of games: FPSs and RTSs.
FPSs honestly haven't changed all that much in years. Sure the graphics have gotten better and there have been minor improvements but honestly an FPS is an FPS.
We played LAN Warcraft 3 (eg tower defense maps). Personally I prefer turn-based strategy games, which are a dying breed (sadly).
But what drove those early LAN gaming sessions was I think two things:
1. Novelty; and
2. Internet connections.
There was a time when multiplayer gaming wasn't possible with the Internet connections of the day. Now it is. The result is less need to drag your computers to someone elses house.
Of course the effect of that is that you can then play with anyone not just your friends, which ironically seems to mean that you just don't do it anymore. Anyone older the school age seems to hate online gaming with strangers as you have to deal with cheaters and kids who have nothing better to do than play 8+ hours a day, which is fine, but it's not fun for the casual gamer.
See why tabletop games work is that tabletop gaming is a social exercise. You get together with friends and play. If you just played online, even with your friends, I don't believe it'd have anywhere near as much stickiness and definitely less adherents.
Another factor is DRM in video games -- why spend 4x$60 on four licenses for a multiplayer video game and hundreds more on hardware, when you could just spend $50 on a board game and have it support four to six people?