5) Did Moriarty Plan To Fail?
“The Final Problem” finally revealed the truth about Moriarty’s apparent resurrection at the end of season 3. He did indeed blow his own brains out in season 2’s finale but, prior to that, he had helped Eurus with her plan to mess with Sherlock, John and Mycroft. Those videos of him saying “Miss me?” were just recorded before his death.
This begs the question: did Moriarty always know he would fail in his plan to force Sherlock to launch himself off the rooftop at St. Barts’ Hospital? If he’d succeeded in killing her brother, Eurus would have been pretty annoyed that he’d mucked up her evil plans. Plus, she does say that Moriarty wasn’t that interested in “staying alive” as long as Sherlock’s life was made a living hell. It’s possible, then, that he knew that Sherlock was planning to fake his death but let it happen and killed himself because he thought Eurus’ plan to make it look like he was still alive was more fun.
Also, while we’re at it, why did Mycroft think that pairing up the two most dangerous people in the world would be in any way a good idea? Yes, Eurus was doing him some favours by deducing where and when terrorist attacks would take place, but he should have expected something bad to happen.