The mid-credit scene in Morbius still grates on some fans, who blame a particular supervillain for the blunder.
In the r/FanTheories subreddit, DarrylTheDudeWayne thinks Kang The Conqueror (Jonathan Majors) is to blame for Vulture’s (Michael Keaton) incongruous appearance in the scene. They wrote, “Kang was responsible for Vulture ending up in the Venom/Sonyverse,” and argued that Kang is most likely the one who sabotaged Doctor Strange’s spell.
OP makes many intriguing points. The appearance of Vulture in the Sonyverse may seem senseless at first glance. But what if his presence is a testament to the magnitude of Kang’s power? What if Kang can override Doctor Strange’s spells so totally that he can transport whomever he pleases to the Quantum Realm? Is it possible that Kang has grown so powerful that he can learn which hexes Doctor Strange is casting and use them to his advantage?
After all, Kang is a genius whose inventiveness knows no limits. Considering that he was the catalyst for the Multiversal War, he is a villain in a league of his own who will stop at nothing to rule its every dimension. OP is spot on that Kang is one of the few characters who could pull an operation like this off.
Furthermore, Kang will need allies to realize his ambition of ruling the Multiverse someday.
While the mid-credit scene may have seemed pointless, chances are it was taken out of context and misunderstood. Imagine if the backstory is anywhere near the scenario envisioned by OP. On the other hand, maybe the point of the scene was to let fans know that anything is possible in the Multiverse.