In Vecna Lives!, the players start the adventure either by playing the great mages of the setting or seeing what happened to them.
In a homebrew of my own, the PCs spent the first part of the initial evening at a citywide wedding party that sealed a truce and alliance ending a decades-long war...only to be snatched up by interdimensional pirates looking for “game” to be put in a hunting preserve...
So I’m familiar with and use the technique you describe. But I also think you took it a bit far. In a Godzilla flick, he and the other kaiju rarely destroy the WHOLE city. A sizable or key portion thereof is sufficient to demonstrate the stakes and get the players oriented on the scaly flying bastard’s demise. Imagine if the dragon had destroyed that city’s main church- the campaign world’s analogue of Notre Dame cathedral...
Because the total destruction of the city, among other things, begs the question of WHY the dragon would utterly destroy a city. Even if chaotic in nature, dragons are intelligent, cunning beings, and would have a motivating force behind laying a town to waste that he or she could otherwise raid and terrorize for decades with a bit of restraint.