How did the Lori-Gibb gang bring Freddy to life?
Because that's how the rules work in A Nightmare on Elm Street franchise:
In A Nightmare on Elm Street (1984):
She plans to take Fred into the real world, and sets up booby traps in her house. Concerned over her influence, Glen's parents prevent the two from meeting. Glen falls asleep at their appointed hour, and Fred kills him and releases his blood in a large fountain in his room, which is witnessed by Glen's mother.
Alone, Nancy puts Marge to bed and asks Don, who is across the street, to break into the house in twenty minutes. In her sleep, she locates Fred at the last second and pulls him out of the dream.
Almost same method used in A Nightmare on Elm Street (2010) to defeat Freddy.
This wikia list his weakness quite well and more prominent one is :
He can also be pulled out of the dream world, in which case, he is mortal, cannot use most of his powers (although he retains some of them like climbing up the ceiling or shapeshifting into his unburnt self, as evidenced in Freddy's Dead), and can die (though, as shown in Freddy's Dead and Freddy vs. Jason) he can withstand slightly more than regular humans do, as he suffers multiple injuries by Maggie and Jason and survives, when anyone else might have been killed by such injuries, but apparently can be killed by injuries serious enough as explosions or decapitation.