He captured
Hurin because he knew where
Gondolin was.
Fingon didn't know where it was.
Morgoth learned of Hurin and Huor's supposed sojourn in Gondolin from spies who heard the rumour of it, after their conversation with Galdor.
It seems surprising that Hurin is always
the one who is captured and it seems this was a long standing story in the mythology, from the Book of Last
Tales,
Turumbar and the Foaloake (BoLT 2) ,
Lay of the Children of Hurin (HoME 3) and of course the Quenta's and Annals of HoME 4 and 5. Of course the story that Huor was the one who went to Gondolin with him only emerged in the course of writing the
Grey Annals (HoME 11), before that it was Haleth (
Annals of Beleriand, Later Quenta Silmarillion, HoME 5) and Handir, grandson of Haleth (HoME 11). The story of
Tuor being Hurin's companion in Gondolin also appears in
Of Tuor and his Coming to Gondolin (U.T) which was written 1951, at the same time when he was re-writing/editing the
Grey Annals. But as I said, I think the notion of Hurin being captured by Morgoth so he could locate Gondolin was firmly embedded in the myth.
Note that the version given in the
Grey Annals was rejected for a later version of him saying 70
Trolls, not 100 Ork's, as is told in the
Published Silmarillion. Even if they were trying to capture him it was sure a great feat anyway. But I think it was his warrior prowess that played a greater part.
The Trolls would have got carried away (And Orks in the version you have citied) and maybe would have been filled with battle-lust, but you must remember that it was the Troll-guard of Gothmog, Gothmog would have been assigned as the one who was going to capture him, as he did. Hurin was 'captured' by hordes of Orks jumping on him, and restricting his movement, so this could be seen as the mode of capture that Morgoth wanted, IMO, Hurin simply just whooped some
Troll but. ( Do you really think Troll's were intelligent enough to understand commands to capture him
)