Android, Windows Phone (the “metro” rewrite from scratch - not the WinCE one), Palm WebOS, etc were all well and truly in development and close to launch and most of them were being developed in the open. Apple who was cutting corners everywhere to leapfrog those products. It took Apple just four years to go from initial planning to a shipping product.

This is ranges from just misleading to factually wrong. WebOS, for example, didn't launch until 2009, 2 years after the iPhone demo in question.

Windows Phone:

In 2008, Microsoft reorganized the Windows Mobile group and started work on a new mobile operating system.

Android:

An early prototype had a close resemblance to a BlackBerry phone, with no touchscreen and a physical QWERTY keyboard, but the arrival of 2007's Apple iPhone meant that Android "had to go back to the drawing board".

For ARM, I have to go with a "sort of?" Apple has been tied to ARM 80's so that's correct, but my phone prior to the first iPhone was one of these bad boys: the Palm Treo. It used a Intel PXA270 312 MHz. In my use, the Treo had better battery life, though admittedly that may just be because I rarely even tried to do things like use the internet on it because it was such a jank experience, so my primary use was planner types of things, texts, and since it was 2005-6, phone calls.

Anyway, back to the poster you responded to:

What competition? At that point it was BlackBerry and WinCE. Oh, and PalmPilot. [sic: by this point they had dropped "Pilot" which was actually a device type, not a company/brand.]

The actual timeline makes it pretty clear that this comment is almost objectively correct. However, even this is not correct because Apple didn't set out to compete with what we considered "smartphones":

He said Apple had set the goal of taking 1 percent of the world market for cellphones by the end of 2008. That may seem small, but with a billion handsets sold last year worldwide, that would mean 10 million iPhones — a healthy supplement to the 39 million iPods that Apple sold last year.

Bold added for emphasis.

Or, you can hear it straight from the horse's mouth: Jobs at the original iPhone keynote.

Anyway, I was alive for all of this, iPhone 10000% caught literally everyone flatfooted.