No where in the article it mentions how did they nail him or how did he do. With Twitter saying that this entire process was done by social engineering some employee and then gaining system access of others by monitoring the process - this seems to have been done by someone with Corporate process understanding and hard to believe it could be a 18 yold.
Seems to me that a person sophisticated enough to social engineer Twitter employees is probably sophisticated enough to social engineer a Tampa teen into place for taking a fall. To me state level targets suggest state level actors and Twitter has been mucking about with state level political operations since at least the Arab Spring almost a decade ago.
Twitter has a lot of powerful people and organizations who have suffered discomfort at its hands. It is hard to swallow the thesis that a Tampa teen succeeded where intelligence agencies have failed despite years of efforts.