Adding on now that I've read the article and this situation is covered:

> The following year, in 2015, the Bitcoin community fractured over a proposal to increase Bitcoin’s block size. A faction led by two Bitcoin developers, Gavin Andresen and Mike Hearn, wanted to make the blocks much bigger to accommodate more transactions. But this was controversial...

> Mr. Back fiercely opposed increasing the block size. In a series of posts on the Bitcoin-dev list, he warned against Mr. Andresen and Mr. Hearn’s proposal in increasingly strident tones.

> Then, out of the blue, Satoshi appeared on the list with an email that neatly dovetailed with Mr. Back’s position. It was the first time Satoshi had been heard from in more than four years, other than a five-word post the previous year denying a Newsweek article’s claim to have unmasked him.

> Many in the Bitcoin community questioned the new email’s authenticity since another of Satoshi’s email accounts had been hacked. But Mr. Back argued that the email sounded real. In a series of tweets, he called Satoshi’s observations “spot on” and “consistent with Satoshi views IMO” and took to quoting from the email.

I now realize that the Satoshi email was after Hal Finney's death so that changes my opinion.

From OP:

> Satoshi supported big blocks in his writings and empowered the pro-big block Gavin when he disappeared

This isn't correct. In fact, the linked email in the article says the opposite https://gnusha.org/pi/bitcoindev/6EC9DDF352DC4838AE9B088AB37...

I have no real interest in this chat, but a quick google makes me agree that Hal Finney was very likely Satoshi. Fits my expectations perfectly and would also explain why it’s a “mystery”, ie some people know but agreed not to reveal it as per Hal or family wishes given their targeting by criminals in the past. Extremely plausible.

I think Back reacts the way he does when being asked if he is the creator of BTC is that he knows it was Finney, and the key is gone.