Slow insert into but fast select query - sql

Question

A select query with join returns results in less than 1 sec(returns 1000 rows: 600 ms) but insert into temp table or physical table takes 15-16 seconds.
tested io performance : a select or insert into without any joins takes sub-second to write 1000 rows.
tried trace flag 1118
tried adding clustered index on the temp table and do insert into with tablock and maxdop hint.
None of these improved performance.
Thanks for all your comments. 6000 to 20000 rows that need to be inserted every 5 seconds from Kafka...
I get the data from kafka into sql server using table type variable
Pass it as a parameter to stored procedure
Load this data joining with other tables into a temporary table #table
I use the #table to merge the data into application table
Found a workaround that helps me achieve the target turnaround time but dont exactly know the reason for the behaviour. As I mentioned in the problem statement, the bottleneck was writing the resultset of the select statement that joins the table variable with various other tables to the temp table.
I put this into a stored prod and returned the execution of the stored proc to a temp table. Now the insert takes less than 1 sec
SELECT
i.Id AS IId,
df.Id AS dfid,
MAX(CASE
WHEN lp.Value IS NULL and f.pnp = 1 THEN 0
WHEN lp.Value = 0 and f.tzan = 1 and f.pnp = 0 THEN NULL
ELSE lp.Value
END) 'FV',
MAX(lp.TS),
MAX(lp.Eid),
MAX(0+lp.IsDelayedStream)
FROM
f1 f WITH (NOLOCK)
INNER JOIN ft1 ft WITH (NOLOCK) ON f.FeedTypeId = ft.Id
INNER JOIN FeedDataField fdf WITH (NOLOCK)
ON fdf.FeedId = f.Id
INNER JOIN df1 df WITH (NOLOCK)
ON fdf.dfId = df.Id
INNER JOIN ds1 ds WITH (NOLOCK)
ON df.dsid = ds.Id
INNER JOIN dp1 dp WITH (NOLOCK)
ON ds.dpId = dp.Id
INNER JOIN dc1 dc WITH (NOLOCK)
ON dc.dcId = ds.dcId
INNER JOIN i1 i WITH (NOLOCK)
ON f.iId = I.Id
INNER JOIN id1 id WITH (NOLOCK)
ON id.iId = i.Id
INNER JOIN IdentifierType it WITH (NOLOCK)
ON id.ItId = it.Id
INNER JOIN ivw_Tdf tdf WITH(NOEXPAND)
ON tdf.iId = i.Id
INNER JOIN z.dbo.[tlp] lp
ON lp.Ticker = id.Name AND lp.Field = df.SourceName AND
lp.Contributor = dc.Name AND lp.YellowKey = tdf.TextValue
WHERE
ft.Name in ('X', 'Y') AND f.SA = 1
AND dp.Name = 'B' AND (i.Inactive IS NULL OR i.Inactive = 0)
AND it.Name = 'T' AND id.ValidTo = #InfinityDate
AND tdf.SourceName = 'MSD'
AND tdf.ValidTo = #Infinity
GROUP BY i.Id, df.Id
OPTION(MAXDOP 4, OPTIMIZE FOR (#Infinity = '9999-12-31 23:59:59',
#InfinityDate = '9999-12-31))