I have theories for you.
the dummy body hanging in 221B at the beginning.
Moriarty has a Sherlock mask, which he wore when he kidnapped the children.
Molly put the Sherlock mask on the dummy.
The cyclist (who is in on it all) knocks John over so he doesn’t realise that it is not Sherlock.
The people all around his body are Sherlock’s homeless network, doing him a massive favour.
wow this is actually perfect