It's crazy how it all seems connected now.
There was a certain event in 'Loki' that actually triggered the events of 'Spider-Man: No Way Home' and 'Doctor Strange in the Multiverse of Madness', Marvel producer Kevin Feige revealed on the red carpet.
"There's always a method to the madness, even in the multiverse, and for Marvel fans, who know that Loki and Sylvie did something at the end of that series, that sort of allowed all this to be possible," Feige explained.
"He Who Remains is gone, and that allowed a spell to go wrong in 'Spider-Man: No Way Home', which leads to the multiverse going quite mad in this."
Feige referred to the death of Kang, also known as He Who Remains, in 'Loki' episode 6. It was the female variant of Loki, Sylvie, who decided to kill He Who Remains, even though she knew that this could potentially lead to a multiverse catastrophe (as it sorta did, judging by the Doctor Strange sequel).
In 'Spider-Man: No Way Home', when Doctor Strange casts his spell to help Peter Parker regain anonymity, it goes horribly wrong, dragging people from other universes, aware of Peter Parker being Spider-Man, into the MCU. At the end of the movie Strange has to erase everyone's memories about him so that the multiverse does not dramatically affect "our" universe – to such an extent that even Peter's best friends and his girlfriend forget about him.
'Multiverse of Madness' seems to reflect the aftermath of Loki and Sylvie's decision even in the movie title, with us to learn more about it as soon as the movie hits screens on May 6.