John was exposed to Eurus for several weeks prior to her shooting him at the end of TLD. Euros moved in on John in T6T. He was her target to get to Sherlock. When the seduction didn’t work, as John rejected an affair, she changed tactics and targeted his psychological treatment. Makes sense that a bit of ‘Manchurian Candidate’ mind manipulation was occurring.
The best thing about this is that John knows this. I mean, TFP is in his head, so HE pictured Eurus as a psycho mind-reprogramming manipulator in his dream, because clever John concluded she must have manipulated him into pouring all of his anger and blame over Sherlock. I love this clever boi.
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