Don't make changes when compiling

Hello! Help is needed. I decided to translate all the text and change the background. I downloaded the sources and made changes to the WLED-main\wled00\data files. (index.htm, index.css, settings.htm, etc.)
Next, in the platformio.ini file, I removed the “;” for the board default_envs = esp32dev.
Then everything is compiled, the firmware is uploaded, but it is unchanged as by default. My changes are not applied((
I am attaching screenshots, one of them shows the changed page.
What could be the reason?

See the “Changing Web UI” section, need to build it separately

https://kno.wled.ge/advanced/custom-features/