Conveying "Jumping the shark"

Question

Reading a review for the new Fast and Furious film I came across the (American) idiom "jumping the shark".

Jumping the shark is an idiom used to describe the moment of a misguided attempt at generating new publicity for something once, but no longer, widely popular; the attempt serves instead to highlight the irrelevance of what it intends to promote. This is especially applicable to television series or other entertainment outlets. https://en.wikipedia.org/wiki/Jumping_the_shark

I was curious if there is an idiomatic way to convey "jumping the shark" as below

“This is Trump’s jump the shark moment,” John Feehery, a former key aide to Republican congressional leaders, told the Daily News. “It’s all downhill from here.”

Answer 1

A few suggestions, although none is a direct replacement:

• Atteindre son apogée: A place from where you can only go downhill. However, unlike "jump the shark", the term is positive.

• Tournant: A significant change in direction. Might be positive or negative.

• Partir en vrille: Lose control.

“This is Trump’s jump the shark moment,...” might then be translated to:

C'est un tournant pour D. Trump,...

À partir de là, D. Trump a commencé à partir en vrille,...

Answer 2

After reading the "jumping the sharks" wikipedia page, and @jiliagre's answer, here are other examples I would like to add (I am not completely sure about my translations though) :

• A un moment donné, il ne savaient plus quoi inventer

At one moment, they ran out of ideas [hence : they started doing stupid things].

• A partir de là, c'est devenu n'importe quoi.

From that point, it became nonsense.

• A partir de ce jour là, ça a viré au (grand) n'importe quoi.

From this day, it went (full) nonsense.