Why destroy Laketown's bridge?

[Macalaure]

It means that Smaug did not like water. So its easy to then see that he would want to be as far away from it as possible. Thus, an attack for the air was his preferred mode of attack and would not land being closer to the water.

Happy now?

You are aware that that quote comes after Smaug found the bridges destroyed? Therefore, it was his preferred mode of attack after whatever mysterious mode of attack he had in mind before. You will find nobody disagreeing on that.