What is this strange error Error:Error converting bytecode to dex: Cause: java.lang.RuntimeException: Exception parsing classes?

Question

Android

Good!
Here, when building my application, I started to pour
Error: Error converting bytecode to dex:
Cause: java.lang.RuntimeException: Exception parsing classes
did not find any reasons, on stackoverflow they wrote what needs to be added to the build.grade file

defaultConfig {
    ...
    multiDexEnabled true
}

yes, the error disappeared, but what was the reason for it?

Answer 1

I'm starting to suspect that most young developers are Boko Haram. I don’t know how else to explain the reluctance to read documentation, articles and books.
Description of the multiDexEnabled parameter in the official documentation. And the first link in Google, for those who can not in English.