The fact they gave up on the Russiagate conspiracy after a while doesn't obviate them pursuing it because they "thought it had teeth" (it didn't) or because the conspiracy theory was believed by "everyone" (it wasn't).
The one fact that showed the entire Russigate investigation was purely a hoax was when Mueller testified before Congress, and someone asked him a question about "Fusion GPS" and Mueller literally claimed he had never heard of that organization before. It proved Mueller to be either 100% completely senile or lying, because that was the KEY organization involved in the KEY document for the ENTIRE case. lol. Unbelievalble.
My gut instinct is that he'd sworn to the Clintons years before that he'd never publicly talk about that firm.
CNN, and countless other outlets, thought there could be teeth there at the beginning. They reported as it went along, and as we found out via Mueller's investigation, there wasn't much to the claims at all, save for a couple of minor tidbits. As it happens, CNN, and countless other outlets, have since reported on the fact that most of it turned out to not be true.
That's about standard for how most media organizations handle shit, right-wing outlets included.
The fact they gave up on the Russiagate conspiracy after a while doesn't obviate them pursuing it because they "thought it had teeth" (it didn't) or because the conspiracy theory was believed by "everyone" (it wasn't).