What really sparked my interest was having WiFi in a chip that only cost maybe 2 usd at the time. Plus, you could find great usb dev boards for less than 5 usd.
If I had this stuff as a teenager, I would've lost my mind...
Yeah, important to remember that the old Wifi module for the Arduino was like 20-30 bucks and was basically just an AT modem that still needed a host Arduino. Barely anybody ever used them that I saw. The original ESP-01 for a couple bucks was a very exciting product for hobbyists just as a serial-to-wifi adapter even with minimal English documentation, and then it went bonkers when they released Arduino support and a package with enough IO to do useful things. Espressif has also been pretty nice to the hobbyist community in general once they realized what they had done.
The first time I saw a 8266 I thought "why am I struggling with Arduino or Raspi if this thing is all I need to make a sensor + wifi mesh". Also being powered through the USB is a plus, lots of unused USB ports around in 24/7 machines.
If I had this stuff as a teenager, I would've lost my mind...