Satoshi and Wright were involved on Bitcoin from the beginning. Satoshi did the tech, Wright did the marketing. It starts off as just another of Wright's wacky business scams, but actually takes off. Satoshi dies, Wright takes advantage by telling everyone he's Satoshi, but can't actually get Satoshi's coins.
We have stories of Wright orchestrating complex staged technology theatre which involves hijacking DNS on a wifi network he controls and forcing an unaltered Electrum client on a clean laptop to connect to bitcoin nodes that he controls to fake the signature verification for Gavin. We're talking about 2 or 3 different MITM attacks necessary to pull off such a stunt, in front of people who obviously understand Bitcoin and are skeptical because of the December story.
I just think the speculation on possible stories for what really happened is getting a little out of hand.
Somebody develops a brand new technology which has wide-ranging implications, from drug enforcement to currency control (and well beyond). Within a few years it's worth billions. But it's developed by somebody with a Japanese pseudonym. Multiple people are unmasked and then debunked as the inventor. Then a serial dodgy geezer, who was previously unasked and debunked, says they are in fact the inventor - but it turns out their evidence is meaningless.
It's the closest thing we have in real life to "Who is Batman?" so of course we're all fascinated.
Perhaps Wright is gambling that Satoshi is dead (for whatever reason, foul play or not). The purpose of his previous (original) Satoshi scam was to ascertain that nobody has access to Satoshi's private keys.
Wright can't get Satoshi's bitcoins, but presumably if people think he is Satoshi, this would help him with his other tax evasion scams he seems to be involved in. Perhaps it doesn't even matter if the tech community immediately realised that he is lying, all he needs is some reasonable belief in the other laypeople he is scamming.
Gavin might have been bought, or Gavin knows that Satoshi is dead, and Wright threatened Gavin, pretending he was the one who killed Satoshi.