We know for a fact that there was intelligence and evidence that Russia was paying bounties to the Taliban to kill US soldiers...They want the US out of the region, and more casualties means less support for our continued involvement.
The options are:
1) Trump was presented the evidence and simply didn't care or chose not to believe it
2) Trump didn't read the memo
3) His aides were reluctant to present him the evidence b/c he wouldn't believe it (as with the Russian 2016 meddling).
Is there a 4th option I'm not considering?