Your vague reference to "they" suggests you are conflating actions by a variety of people and organizations. Point to an individual who knowingly stated a clear falsehood.
The so-called intelligence experts, the whitehouse, and Biden himself, as I've already said. There is nothing vague about it.
The Russian investigation was not a "hoax", because it was initiated as a result of a clear crime (Russians stealing information from DNC servers). A Trump campaign had knowledge of the crime before the emails were made public, and he lied about it. Additional lies were told by other campaign officials during the investigation - it would have been derelict to ignore this. Russian active measures to help Trump were well known during the 2020 campaign, and this was a major factor in wariness of media outlets at reporting it, and in the judgement of the former intelligence officers. It's pretty ironic that Russia's assistance in 2016 backfired on Trump's desire to spread irrelevant dirt in 2020.
Julian Assange denied the emails came from Russia. Shawn Henry of Crowdstrike admitted under oath that there was no evidence the information was exfiltrated. The US government dropped the case against the Internet Research Agency. It was a bunch of hokum, a hoax, and you're still falling for it.
None of the signatories of the letter lied. The letter said they were "suspicious of Russian involvement", that it was "consistent with Russian objectives", and "We do not know whether these press reports are accurate". Of course the Biden campaign would use this analysis to maximum advantage, just like the Trump campaign would try to maximize the NY Post story to their maximum advantage.
The author of the letter, Former acting CIA Director Michael Morell, asking John Brennan to sign the letter in an email said that he wanted to give Joe Biden a talking point in the debate.
"Trying to give the campaign, particularly during the debate on Thursday, a talking point to push back on Trump on the issue."
https://justthenews.com/sites/default/files/2023-05/MorellBrennanEMailOct2020.pdf
Given this activity in light of their fake concern that "each of us believes deeply that American citizens should determine the outcome of elections", it appears they lied. It was clearly a political operation used to influence the election, to help the Biden campaign and cripple Trump. I'm interested to hear how you'll spin it.