Problems with cordova-plugin-firebase

The build is failing after i added cordova-plugin-firebase. Every time i get a different error. I noticed that the plugin is changing my google-service.json as well. The most error i am getting is the following:

 Execution failed for task ':app:fabricGenerateResourcesDebug'.
> Crashlytics Developer Tools error.
app:fabricGenerateResourcesDebug FAILED
ERROR - Crashlytics Developer Tools error.
java.lang.IllegalArgumentException: Crashlytics found an invalid API key: 
null.
Check the Crashlytics plugin to make sure that the application has been 
added successfully!
Contact [email protected] for assistance.

I have no idea why is this tool needed and what has io fabric to do with it. I haven't installed or migrated anything from io fabric. here are my package.json dependencies:

"@angular/animations": "^8.1.2",
"@angular/common": "^7.2.2",
"@angular/core": "^7.2.2",
"@angular/forms": "^7.2.2",
"@angular/http": "^7.2.2",
"@angular/platform-browser": "^7.2.2",
"@angular/platform-browser-dynamic": "^7.2.2",
"@angular/router": "^7.2.2",
"@ionic-native/core": "^5.0.0",
"@ionic-native/fabric": "^5.12.0",
"@ionic-native/firebase": "^5.0.0",
"@ionic-native/social-sharing": "^5.11.0",
"@ionic-native/splash-screen": "^5.0.0",
"@ionic-native/status-bar": "^5.0.0",
"@ionic/angular": "^4.1.0",
"@ionic/storage": "^2.2.0",
"angularfire2": "^5.2.1",
"cordova-android": "^8.0.0",
"cordova-plugin-androidx": "^1.0.2",
"cordova-plugin-androidx-adapter": "^1.1.0",
"cordova-plugin-firebase": "^2.0.5",
"cordova-plugin-x-socialsharing": "^5.4.7",
"cordova-sqlite-storage": "^3.2.1",
"cordova-support-google-services": "^1.3.1",
"core-js": "^2.5.4",
"es6-promise-plugin": "^4.2.2",
"firebase": "^6.3.1",

*my app-level build gradle dependency:

apply plugin: 'com.android.application'

buildscript {
  repositories {
    mavenCentral()
    google()
    jcenter()
   }

  dependencies {
    classpath 'com.android.tools.build:gradle:3.3.0'
   }
 }

 dependencies {
 implementation fileTree(dir: 'libs', include: '*.jar')
implementation 'com.google.firebase:firebase-core:17.0.0'
// SUB-PROJECT DEPENDENCIES START
implementation(project(path: ":CordovaLib"))
implementation "com.google.android.gms:play-services-tagmanager:+"
implementation "com.google.firebase:firebase-core:+"
implementation "com.google.firebase:firebase-messaging:+"
implementation "com.google.firebase:firebase-config:+"
implementation "com.google.firebase:firebase-perf:+"
implementation "androidx.annotation:annotation:1.0.0"
implementation "androidx.legacy:legacy-support-v4:1.0.0"
// SUB-PROJECT DEPENDENCIES END
}

*my project level build-gradle dependencies:

   dependencies {

    // NOTE: Do not place your application dependencies here; they belong
    // in the individual module build.gradle files
    classpath 'com.android.tools.build:gradle:3.3.0'

    classpath 'com.google.gms:google-services:4.1.0' // google-services 
dependency from cordova-plugin-firebase

    classpath 'io.fabric.tools:gradle:1.25.4' // fabric dependency from 
cordova-plugin-firebase
    }

project properties:

target=android-28
android.library.reference.1=CordovaLib
android.library.reference.2=app
cordova.gradle.include.1=cordova-android-firebase-gradle-release/promocat- 
cordova-android-firebase-gradle-release.gradle
cordova.gradle.include.2=cordova-plugin-firebase/promocat-build.gradle
cordova.system.library.1=com.google.android.gms:play-services-tagmanager:+
cordova.system.library.2=com.google.firebase:firebase-core:+
cordova.system.library.3=com.google.firebase:firebase-messaging:+
cordova.system.library.4=com.google.firebase:firebase-config:+
cordova.system.library.5=com.google.firebase:firebase-perf:+
cordova.system.library.6=androidx.annotation:annotation:1.0.0
cordova.system.library.7=androidx.legacy:legacy-support-v4:1.0.0
cordova.gradle.include.3=phonegap-plugin-multidex/promocat-multidex.gradle

after building, the plugin is changing my google-service.json that i downloaded from firebase to this:

"project_info": {
"project_number": "123",
"firebase_url": "https://cordova-plugin-firebase.firebaseio.com",
"project_id": "cordova-plugin-firebase",
"storage_bucket": "cordova-plugin-firebase.appspot.com"
 },
"client": [
{
  "client_info": {
    "mobilesdk_app_id": "1:123:android:123",
    "android_client_info": {
      "package_name": "com.github.cordova_plugin_firebase"
    }
  },
  "oauth_client": [
    {
      "client_id": "123.apps.googleusercontent.com",
      "client_type": 3
    }
  ],
  "api_key": [
    {
      "current_key": "123"
    }
  ],
  "services": {
    "analytics_service": {
      "status": 1
    },
    "appinvite_service": {
      "status": 1,
      "other_platform_oauth_client": []
    },
    "ads_service": {
      "status": 2
    }
  }
}
],
"configuration_version": "1"
 }