The first blight to hit Brontitall was the blight of the robots. Instead of trying to take over the planet, they actually liked the inhabitants, which for the said inhabitants was ghastly. But then they'd been programmed to.

Then one day, the sky boiled in amost improbable way. A gigantic vision appeared in the sky. A man (Arthur Dent) with a Nutrimatic cup, and you said...

Listen you stupid machine, it tastes filthy, take this cup back. So I'm a masochist on a diet then? Shut up!

In a moment the Brontitallians realised the truth. Just because the wretches liked them, the Brontitallians didn't have to like them back. And that night every last one of the robots was rounded up. And the robots were set to work to build the status as an eternal reminder. After which they were sent to a slave planet where they're doing a very useful job making continent toupes. Toupes for worlds where they've used up all the forests.

Incidentally, the statue's cup stays where it is unsupported because it's artistically right. The Law of Gravity isnt as indiscriminate as people think.