Mongoose populate not returning the desired data neither an error to identify the problem

I have the followings models:

The article one:

const mongoose = require('mongoose');

const articlesSchema = new mongoose.Schema({
    isFixed: { type: Boolean, default: false },
    author: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'Users',
    },
    comments: [
        {
            type: mongoose.Schema.Types.ObjectId,
            ref: 'Comment',
        },
    ],
    updatedAt: { type: Date, required: true, default: Date.now },
    views: { type: Number, default: 0 },
    likes: { type: Number, default: 0 },
    title: { type: String, required: true },
    body: { type: String, required: true },
    images: { type: Array, required: true },
});

module.exports = mongoose.model('Article', articlesSchema);

and the comments that the users can leave in each article created.

const mongoose = require('mongoose');

const commentSchema = new mongoose.Schema({
    article: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'Article',
        required: true,
    },
    user: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'User',
        required: true,
    },
    body: { type: String, required: true },
    createdAt: { type: Date, default: Date.now },
});

module.exports = mongoose.model('Comment', commentSchema);

However when using the fuction to populate the article with its comments no error ocurrs but no comments are returned, even though being present in the mongoDB. I’ve tried to analyse many times but couldnt find the reason why the comments array length is 0(no comments). Even tried to use ChatGPT to check the code and it says that the code seems right. Do you guys have any suggestions? Even blog posts talking about this “relational part” would be very useful. But if you have some time to check the code and see if it is really okay i would be very grateful!
Function to populate:

async function getArticle(id) {
        const article = await Articles.findOne({ _id: id })
            .populate([
                {
                    path: 'author',
                    select: 'username isAdmin -_id',
                },
                {
                    path: 'comments',
                    select: '_id',
                },
            ])
            .exec();
        return article;

}