EF Core not fetching sub-entities by Id [Answered]

I'm kinda new to EF Core so maybe the terminology is not right.

I have the following models:

Player:

public sealed class Player
{
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public string Id { get; set; } = null!;
    public string Username { get; set; } = null!;
    public Group Group { get; set; } = null!;
}

Group:

public sealed class Group
{
    public string Id { get; set; } = null!;
    public string? ParentId { get; set; }
    public string Name { get; set; } = null!;
    public string[] Permissions { get; set; } = Array.Empty<string>();
}

And tables:

Players:

CREATE TABLE IF NOT EXISTS public.players
(
    "Id" character varying(36) COLLATE pg_catalog."default" NOT NULL,
    "Username" character varying(64) COLLATE pg_catalog."default",
    "GroupId" character varying(36) COLLATE pg_catalog."default",
    CONSTRAINT players_pkey PRIMARY KEY ("Id")
)

TABLESPACE pg_default;

ALTER TABLE IF EXISTS public.players
    OWNER to postgres;

Groups:

CREATE TABLE IF NOT EXISTS public.groups
(
    "Id" character varying(36) COLLATE pg_catalog."default" NOT NULL,
    "ParentId" character varying(36) COLLATE pg_catalog."default",
    "Name" character varying(64) COLLATE pg_catalog."default",
    "Permissions" character varying(64)[] COLLATE pg_catalog."default",
    CONSTRAINT groups_pkey PRIMARY KEY ("Id")
)

TABLESPACE pg_default;

ALTER TABLE IF EXISTS public.groups
    OWNER to postgres;

It works fine when adding a player, it inserts the GroupId as i would expect it to, but when fetching

var player = await _context.Players.FirstOrDefaultAsync(x => x.Id == request.Id);

Group is null

Why is this happening?