Why is Newt Scamander not credited for defeating Grindelwald too?

Question

If disarming the guy, capturing him, and getting him thrown in prison could be considered “defeating” him, why isn't Newt Scamander famous for defeating Gellert Grindelwald the way that Dumbledore is?

Answer 1

He was credited

Rita Skeeter's biography of Newt credited him with capturing Grindelwald (among other things).

I am not yet in a position to tell the full story of my activities during the two decades that Gellert Grindelwald terrorised the wizarding world. As more documents become declassified over the coming years, I will be freer to speak openly about my role in that dark period in our history. For now, I shall confine myself to correcting a few of the more glaring inaccuracies in recent press reports.

In her recent biography Man or Monster? The TRUTH About Newt Scamander, Rita Skeeter states that I was never a Magizoologist, but a Dumbledore spy who used Magizoology as a ‘cover’ to infiltrate the Magical Congress of the United States of America (MACUSA) in 1926.

This, as anyone who lived through the 1920s will know, is an absurd claim. (...)

It is true that I was the first person ever to capture Gellert Grindelwald and also true that Albus Dumbledore was something more than a schoolteacher to me. More than this I cannot say without fear of breaching the Official Magical Secrets Act or, more importantly, the confidences that Dumbledore, most private of men, placed in me.

_{(Fantastic Beasts and Where To Find Them (2017 edition) - Foreword by the Author}

Prior to this he was largely uncredited due to the events being classified by the magical government(s).

Answer 2

Dumbledore ended Grindelwald’s reign - Newt’s capture didn’t.

In Elphias Doge’s biography of Dumbledore, he explains the significance of this duel to wizarding society. While he is a friend of Dumbledore’s, and may as such have a tendency to overstate things, this seems to be fairly close to the attitude of the wizarding world in general.

“They say, still, that no wizarding duel ever matched that between Dumbledore and Grindelwald in 1945. Those who witnessed it have written of the terror and the awe they felt as they watched these two extraordinary wizards do battle. Dumbledore’s triumph, and its consequences for the wizarding world, are considered a turning point in magical history to match the introduction of the International Statute of Secrecy or the downfall of He Who Must Not Be Named.”
_{^{Harry Potter and the Deathly Hallows, Chapter 2 (In Memoriam)}}

Just as important to its significance, if not more, is the resulting consequences that Grindelwald’s permanent defeat and imprisonment had for the wizarding world.

Newt isn’t credited like Dumbledore because he just stalled him.

When Dumbledore defeated Grindelwald, that was the end of the wizarding world’s Grindelwald-related troubles. Conversely, when Newt helped capture Grindelwald and got him thrown into prison by MACUSA, that didn’t stop Grindelwald’s reign of terror for very long at all. Grindelwald escapes soon after, and continues his plan.

It’s called Fantastic Beasts: The Crimes of Grindelwald
Straight away the title says that Grindelwald (Johnny Depp) will be a big focus in the second film, after having been unmasked in Fantastic Beasts and Where to Find Them. Clearly his capture by MACUSA won’t last for very long, and Grindelwald is still intent on exposing the wizarding community to the non-magical world.

So, what will he do next? As the title suggests, not nice things. Grindelwald escapes custody and sets about gathering followers to his cause. What many of his new devotees don’t suspect is that his true intention is to raise pure-blood wizards up to rule over all non-magical beings.

We know from the Harry Potter books that Grindelwald’s ascent represented a dark time for the wizarding world – much like the rise of Lord Voldemort. So, things are about to get serious.
_{^{Everything we know about Fantastic Beasts: The Crimes of Grindelwald so far - Pottermore}}

That makes it clear that Newt helping MACUSA capture Grindelwald was nowhere near the end of the wizarding world’s Grindelwald troubles. In fact, it’s stated that “things are about to get serious”, meaning the worst is yet to come.

Another feature on Pottermore also makes it clear that this wasn’t much of an obstacle to Grindelwald.

With the help of Magizoologist Newt Scamander, Grindelwald was caught by MACUSA. Still intent on overthrowing the Statute of Secrecy, rules that encouraged wizards to hide from the non-magical community, Grindelwald didn’t let being arrested stop his twisted quest.
_{^{Grindelwald: the story so far - Pottermore}}

The capture by Newt and MACUSA didn’t even stop him for long.

Newt’s effort doesn’t even look like it slowed Grindelwald’s rise for long. The next movie will be taking place in 1927, so it’s likely that that’s also the year Grindelwald escapes from MACUSA custody, probably just a few months after being captured (unless the next movie spans more than one year and he escapes later).

It is set straight after the first film
The film takes place in 1927, just a few months after Newt’s first adventure. So, we’re still deep in the Roaring Twenties but the characters will obviously have bigger fish to fry than taking in the delights of the decade.
_{^{Everything we know about Fantastic Beasts: The Crimes of Grindelwald so far - Pottermore}}

We don’t know yet if Newt has a role in Grindelwald’s final defeat.

The Fantastic Beasts franchise hasn’t covered the famous duel between Dumbledore and Grindelwald yet. It’s all but confirmed that it’ll be featured in the final movie - the series follows Grindelwald’s rise and the final movie is already said to be set in 1945, the year of that duel. As of now, we don’t know what role, if any, Newt played in that final defeat of Grindelwald, and if it’s something that he reasonably should have been credited for somewhere in the seven books.