“Stefan Halper”’s name was leaked on purpose to make it look like that was the informant, the only one. Maybe to get people to stop looking for the real informant(s).
This is my opinion too. They picked the most Republican guy in on it, Halper, to make it seem like something routine.
In fact, there were multiple people, pulling various angles, from which they intended to implicate, indict, and jail Trump and all of his associates as revenge for even attempting to challenge DC power.
But they lost the election.