Why isn't STUFF and FOR XML PATH not concenating?

Question

I have these two tables

CREATE TABLE [dbo].[Things](
    [testid] [int] NOT NULL,
    [testdesc] [varchar](10) NULL
) ON [PRIMARY]

CREATE TABLE [dbo].[ThingsStaging](
    [otherid] [int] NOT NULL,
    [testid] [int] NOT NULL
) ON [PRIMARY]

INSERT INTO [dbo].[Things] ([testid], [testdesc]) VALUES (1, N'Stuff')
INSERT INTO [dbo].[Things] ([testid], [testdesc]) VALUES (2, N'Things')
INSERT INTO [dbo].[Things] ([testid], [testdesc]) VALUES (3, N'Orcs')
INSERT INTO [dbo].[Things] ([testid], [testdesc]) VALUES (4, N'Grubs')
INSERT INTO [dbo].[Things] ([testid], [testdesc]) VALUES (5, N'Shrooms')

INSERT INTO [dbo].[ThingsStaging] ([otherid], [testid]) VALUES (1, 1)
INSERT INTO [dbo].[ThingsStaging] ([otherid], [testid]) VALUES (1, 2)
INSERT INTO [dbo].[ThingsStaging] ([otherid], [testid]) VALUES (1, 3)
INSERT INTO [dbo].[ThingsStaging] ([otherid], [testid]) VALUES (2, 3)
INSERT INTO [dbo].[ThingsStaging] ([otherid], [testid]) VALUES (2, 4)

;with allThings(otherid, descs)
as 
(
    select ts.otherid ,
    stuff ((select ', ' + blah.testdesc  as [text()]
            from (
                select distinct t.testdesc 
                from Things as t
                where t.testid = ts.testid ) as blah 
                for xml path('')), 1, 1, '') as stuffs
    from ThingsStaging as ts 
)
select *
from allThings 

Now when run this query, I get

otherid stuffs
1    Stuff
1    Things
1    Orcs
2    Orcs
2    Grubs

But I should get:

otherid     stuffs
1     Stuff, Things, Orcs
2     Orcs, Grubs

I'm not understanding what I'm doing wrong.

Answer 1

I understand what I did wrong. Code will explain better.

select otherid, stuff((select ', ' + t.testdesc as [text()]
                        from Things as t
                        inner join ThingsStaging as its on t.testid = its.testid
                        where its.otherid = ts.otherid
                        for xml path('')), 1, 1, '') as descs
from ThingsStaging as ts
group by otherid