I had a Palm Pilot when they were the cool thing and connectivity was the biggest issue. Syncing had to be a deliberate process, which meant it didn't necessarily happen frequently, which meant that things like calendaring and even news weren't really all that useful.

The iPhone came out just as WiFi had become pretty ubiquitous and a reasonable data plan was something that could be negotiated. And, even so, you could argue that the iPhone didn't really take off for a few more years.

(The iPod before it had a somewhat similar trajectory. It wasn't obviously a game-changing device from day one.)

ADDED: Connectivity was an issue with the iPod too. It didn't matter that much for music. But anything that required timely updates, such as podcasts, didn't work as well.

Cellular data was technically widely available for years before iPhones (see e.g. GPRS for the tech, adopted in 2000), albeit very expensive.

Apple changed that. They negotiated a special contract with AT&T and for a year or so the first iPhone was the only phone in the US with unlimited data plan.

I had unlimited 3G data on a phone on AT&T's network in 2006, and it was even cheaper than the special iPhone data plan. They didn't recognize my phone's IMEI as a "smart phone" or PDA despite running Symbian so adding unlimited data was $15/mo. Unlimited data on a smart phone or PDA was $30/mo additional on the line. It was there, it just wasn't popular.

Sprint had unlimited 2G “Vision” data as far back as 2001. You could “stream” live video from 10-12 cable channels at 1fps. By 2005 you could stream video at 15fps.

https://www.sprint.com/business/program/newsletter/march05/p...

Also capacitive touchscreens. The resitive ones of older Smartphones wouldn't have worked for the revolutinary UI

Bad resistive screens are bad, but good ones are better than capacitive because they work with styluses or when you're wearing gloves. The Nokia N900 had an absurdly good one.

Apple heavily marketed capacitive screens as an asset, so people who haven't every used a quality resistive screen still carry that around internally.

In about 2002, I had a Handspring Visor Prism, running PalmOS. I bought the VisorPhone, which was a cellular phone add-on that plugged into the back. It was somewhat ungainly, and didn't work well as a voice phone. It also had a separate battery, so you had to charge it on its own. I could use it as a cellular modem, but there wasn't a good practical use case for it, because there were only half-baked web browsers and few apps that used data. You could dial in to your desktop computer over the modem and sync remotely. It was fairly useless, but was the early precursor of what eventually became the Treo, and showed that the combination of cell phone and PDA was a good idea.