Why is css from libraries not inserted into the common css file in wepback?

Question

css

I'm trying to set up webpack to develop a vue app. When I build the application, all the styles in the components and sсss files that I wrote get into the app.css file. But if I connect a vue component or any library (for example, sweetalert2) that has its own styles in a js or vue file, they are inserted into the style tag at the top of the page. Is it possible to do something so that they are also added to the app.css file, and not to the style tag ???
webpack.common.js

const path = require('path');
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const VueLoaderPlugin = require('vue-loader/lib/plugin');
const devMode = process.env.NODE_ENV !== 'production';

module.exports = {
  entry: ['./src/js/app.js', './src/sass/app.scss'],
  module: {
    rules: [{
        test: /\.(png|jpeg|jpg|gif|svg)$/,
        loader: 'file-loader',
        options: {
          outputPath: 'resources',
          name: '[folder]/[name].[ext]',
        }
      },
      {
        test: /\.(eot|ttf|woff|woff2)$/,
        loader: 'file-loader',
        options: {
          outputPath: 'resources/fonts',
          name: '[folder]/[name].[ext]',
        }
      },
      {
        test: /\.css$/,
        use: [
          devMode ? 'style-loader' : MiniCssExtractPlugin.loader,
          {
            loader: 'css-loader',
            options: {
                sourceMap: true
            }
          },
          "postcss-loader",
        ],
      },
      {
        test: /\.scss$/,
        use: [
          devMode ? 'style-loader' : MiniCssExtractPlugin.loader,
          {
            loader: 'css-loader',
            options: {
                sourceMap: true
            }
          },
          "postcss-loader",
          {
            loader: 'sass-loader',
            options: {
              sourceMap: true
            }
          },
        ],
      },
      {
        test: /\.sass$/,
        use: [
          devMode ? 'style-loader' : MiniCssExtractPlugin.loader,
          {
            loader: 'css-loader',
            options: {
                sourceMap: true
            }
          },
          "postcss-loader",
          {
            loader: 'sass-loader',
            options: {
              indentedSyntax: true,
              sourceMap: true
            }
          },
        ],
      },
      {
        test: /\.vue$/,
        loader: 'vue-loader',
        options: {
          esModule: true,
          extractCss: true,
        }
      },
      {
        test: /\.js$/,
        use: 'babel-loader',
        exclude: /node_modules/,
      }
    ]
  },
  resolve: {
    alias: {
      'vue$': 'vue/dist/vue.common.js',
      'res': path.join(__dirname, './src/resources'),
      'root': path.join(__dirname, './src/js')
    },
    extensions: ['*', '.js', '.vue', '.json']
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: "css/app.css",
    }),
    new VueLoaderPlugin()
  ],
}

webpack.dev.js

const path = require('path');
const merge = require('webpack-merge');
const common = require('./webpack.common.js');

module.exports = merge(common, {
  output: {
    path: path.resolve(__dirname, './dist'),
    filename: 'js/app.js',
    publicPath: '/',
    chunkFilename: 'js/[name].js'
  },
  mode: 'development',
  devtool: 'inline-source-map',
  devServer: {
    historyApiFallback: true,
    noInfo: true,
    overlay: true
  },
});

webpack.prod.js

const OptimizeCSSAssetsPlugin = require("optimize-css-assets-webpack-plugin");
const UglifyJsPlugin = require('uglifyjs-webpack-plugin');
const path = require('path');
const merge = require('webpack-merge');
const common = require('./webpack.common.js');


module.exports = merge(common, {
  output: {
    path: path.resolve(__dirname, '.././static'),
    filename: 'js/app.js',
    publicPath: '/static/',
    chunkFilename: 'js/[name].js'
  },
  mode: 'production',
  devtool: 'source-map',
  optimization: {
    minimizer: [
      new OptimizeCSSAssetsPlugin({}),
      new UglifyJsPlugin({
        sourceMap: true,
      })
    ]
  },
});

Library connection code

import swal from 'sweetalert2'
import vSelect from 'vue-select'

If these lines are removed, then the style tags are not added to the dom