I have like 10 ESP32's lying around my house, they're fun to tinker with, but my Raspberry Pis get a lot more attention from me because there is a substantially lower cognitive overhead with them than the ESPs. If I had a plan on selling my stuff, then yeah, the Raspberry Pi might be overkill and I'd consider going for an MCU module. However, for a fun little DIY project, I don't see how an RPi is a problem.
EDIT: Realized I forgot to mention another point; not everyone really wants to muck with pointer arithmetic for simple things; this app was written in Python, and as far as I know, the ESP32 chips are mostly C/Arduino; I realize that there exists NodeMCU and such variants, but due to the Raspberry Pi being "Just a computer", you have access to virtually every language under the sun.
Easier than what? Considering you have to use the already ill-suited for UI HTML/CSS/JS cesspit, I'd say Electron is a lot worse for the "simple desktop app" than something like Lazarus.
If this was a commercial project, I would agree completely (and from a BOM cost, the manufacturer would be a lot better off investing the time in the dev on a microcontroller)
μPython is fine, but typically a programming language is about more than just the language.
All things you basically don't need for a little project like this.
The catches are a) you don't have a lot of memory, and b) you have to watch little flickering LEDs to know if your app installed correction.
They're designed for different things though - if you wanted a battery powered version that updated on a button press else slept, ESP, if you want live updates all the time, Pi is fine!
The Pi0W probably won't run a day on the same battery.
http://www.geekstips.com/wp-content/uploads/2017/10/esp32-po...
vs
https://raspi.tv/2017/how-much-power-does-pi-zero-w-use
Considering that he pi as way more ram, an SD card and a GPU, and is running 4 times as fast.
the important take away is that they have different use cases.
Though I do agree it depends on your use case, if you're plugged into the wall, a Pi0 might be the better option.
I much prefer using an ESP32 for something like this because I don't have to deal with installing distro's, updates, etc.