Even if Trump didn't know (unlikely), his Chief of Staff most assuredly did:
A former American official said the national security adviser, Robert C. O’Brien, and the president’s chief of staff, Mark Meadows, would have been involved in any decision to brief Mr. Trump on Russia’s activities, as would have the intelligence analyst who briefs the president. The director of the C.I.A., Gina Haspel, might have also weighed in, the former official said.
Ms. McEnany cited those three senior officials in her statement saying the president had not been briefed.
The most likely scenario is that Trump was (verbally) briefed on the issue, as well as having it included in his daily intelligence packets (which he probably didn't read). But whether Trump knew or not, his current position of, "I don't believe it, it's not credible," is a direct assault on the integrity of our intelligence community and Special Operations who put themselves in harm's way to uncover this deadly plot:
United States intelligence officers and Special Operations forces in Afghanistan alerted their superiors as early as January to a suspected Russian plot to pay bounties to the Taliban to kill American troops in Afghanistan, according to officials briefed on the matter. They believed at least one U.S. troop death was the result of the bounties, two of the officials said.
The crucial information that led the spies and commandos to focus on the bounties included the recovery of a large amount of American cash from a raid on a Taliban outpost that prompted suspicions. Interrogations of captured militants and criminals played a central role in making the intelligence community confident in its assessment that the Russians had offered and paid bounties in 2019, another official has said.
Armed with this information, military and intelligence officials have been reviewing American and other coalition combat casualties over the past 18 months to determine whether any were victims of the plot. Four Americans were killed in combat in early 2020, but the Taliban have not attacked American positions since a February agreement to end the long-running war in Afghanistan.
Two officials said the information about the bounty hunting was “well known” among the intelligence community in Afghanistan, including the C.I.A.’s chief of station and other top officials there, like the military commandos hunting the Taliban. The information was distributed in intelligence reports and highlighted in some of them.
The assessment was compiled and sent up the chain of command to senior military and intelligence officials, eventually landing at the highest levels of the White House.
Regardless of how you feel about a war that should have ended many years ago, these folks did their job. They discovered the bounties, and reported that all the way up to the civilian leadership. Who did absolutely nothing, and are now denying they even knew about it. And now they're forced to watch as Trump pushes for Russia to be allowed back in the G-7 (8), which represents literally Trillions in economic access.