President Trump should have learned it along with everyone else who watched or listened to the confirmation hearings. If he was really that much out of the loop its on him, not on Jeff Sessions.
And I don’t believe it for a minute. President Trump is a detail man and he knew all the implications and likely laterramifications.
Do you have any actual evidence that Trump has nothing better to do than sit around watching hearings? Do you have one good reason why, if Sessions were seriously considering recusal, he wouldn’t have communicated that directly to his boss?