Given Steve Jobs' character, there may be another reason behind it: that year, before the decision to stop supporting Flash, Adobe broke their agreement with Apple by releasing Photoshop for PCs before the version for Mac for the first time. This could sound as a conspiracy teory, and I don't know how much evidence we have that this might have been the reason (or one of the reasons) behind the decision. But, given Jobs' personality, I think this is plausible.
We should also consider that, having Flash support, would have opened the door to non-Apple-approved apps running on iPhones, something that Apple has always strenously opposed. All-in-all, at the time I got the feeling that the technical reasons provided by Jobs weren't the main reasons behind the decision.
Flash and open source actionscript allowed devs to completely circumvent the Apple App Store. That was a direct threat to the iOS business model at the time.
> Given Steve Jobs' character, there may be another reason behind it: that year, before the decision to stop supporting Flash
Flash was never supported on iOS; Steve's letter was to confirm Apple wasn't ever going to support Flash on iOS; it remained available on MacOS.
I don't think the Photoshop thing had any affect on supporting Flash on iOS.
You're right, I did a quick search and apparently they still considered supporting it though [0], but they didn't they the results they were hoping for.
[0] https://9to5mac.com/2021/04/27/apple-tried-to-help-adobe-bri...