The Local has listed reasons for why Swedes are good at esports. They are listing factors as a strong gaming culture, early access to broadband, many Swedish gaming idols, Swedes watch esports a lot, DreamHack started in Sweden and it is also seen as a career path.
Another factor that I also think has been important, is that Sweden from the middle of the 90s had tax rules that made it beneficial for companies to subsidize personal computers for their employees. That way many homes had access to state of the art gaming computers with internet access early on. I remember buying a new powerful computer every other year or so thanks to this.
With so many computers in Swedish households, it is no wonder that Sweden also had many early game developers. Digital Illusions (DICE), Paradox Interactive, Massive Entertainment, King, Starbreeze, MindArk and Mojang, for instance.
(Photo by Caspar Rubin at Unsplash)