Mongoose populating virtual properties not present in object

Not sure whether I am missing something but cant get populating virtuals to show up in object; getter-setter virtuals are fine.

Minimal example:

Schema setup:

    userSchema = new mongoose.Schema(
    {
      _id: String,
      firstName: String,
      lastName: String,
      followingIds: [String],
    },
    {
      toObject: { virtuals: true, getters: true },
      toJSON: { virtuals: true, getters: true },
    }
    ).pre("findOne", function () {
      this.populate("followedByIds");
    });
    userSchema.virtual("fullName").get(function () {
      if (this.firstName && this.lastName) {
        return `${this.firstName} ${this.lastName}`;
      }
      return this.firstName || this.lastName || undefined;
    });
    userSchema.virtual("followedByIds", {
      type: [String],
      ref: "Users",
      localField: "_id",
      foreignField: "followingIds",
    });
    mongoose.model("Users", userSchema, "users");

Now if I call user = await this.User.findOne({ _id: some_user_id});, console.log(user.followedByIds) actually has correct values - showing that followedByIds is correctly populated (i.e., containing User objects that follows this particular user). However, if I just console.log(user) then followedByIds field simply does not show up! Moreover, trying to res.status(200).send(user) also won't sent over followedByIds field.

However, fullName field works perfectly. It shows up when I console.log(user) and it can also be sent over to client.

I searched over the internet but found nothing. Please advise. Relevant packages:

"mongoose": "^6.5.2",
"express": "^4.18.1",
"typescript": "^4.7.4"