人気がガタ落ちって英語でなんて言うの？

When a bird or even a person dives into the water, their trajectory (because of gravity) is always virtually downward, although some lateral distance may be covered from the momentum of pushing off from the starting position. The trajectory, if represented in a drawing, would show a line heading downwards in a virtually straight line. In terms of a sales chart, such decline in performance may be described as 'having taken a dive.' "Sales of this product have taken a dive."

to be selling - this means that a product is selling quickly or fairly well the demand for a product - this means the consumer demand or the amount of consumers who request a product plummet - this means to drop dramatically/sharply

▪ The popularity of the product disappeared overnight. "disappeared" means it vanished. This sentence indicates that the popularity of the product fell quickly or it became less popular in a very short time.

(idioms) are very useful in scenarios where we want to punch home the point! Dropped like a stone... Went through the floor ....Hit rock bottom! These are all very dramatic images of something falling sharply;-D

This product is no longer as popular as it was before. It lost it's popularity seemingly overnight. The popularity of this product took a nose dive. This means it was popular but then it went downhill and the popularity of the product fell. Usually this expression is used to explain that it seemed to happen abruptly or seemingly overnight.

When something is not as popular and falls sharply by a large amount of popularity (how popular it is) is said to 'plummet' how popular a product is also relates to how much sales there will be so you could also say 'the sales of the product have plummeted'

Most products come into the market then leave sooner than others do. Some products stay on the shelf for a very long period as they are popular and highly in demand. Newer products might not have as much staying power as they might not be a necessity for customers or customers don't yet see the value in the product. We can also say: The product lost its following very quickly. The product's reputation plummeted Plummet: to drop very fast Sunk: to drown, drop Value: worth or importance Reputation: how something is viewed, opinions held about something or someone. Staying power: maintain a certain level