External GPUs didn't catch on earlier because Thunderbolt is the only viable standardized interface for them, and Intel refused to certify eGPU products based o

External GPUs didn't catch on earlier because Thunderbolt is the only viable standardized interface for them, and Intel refused to certify eGPU products based on TB1 or TB2. TB3 is the tipping point where Intel decided there's enough bandwidth to make it a smooth experience, and put their weight behind the idea.