[C19fan]

I have read Beau Brummell is credit with making it fashionable to wear trousers instead of breeches.

[Daveinyork]

I’ve read it was the French revolution that replaced the breeches with the trousers, sans-culottes, without breeches. The breeches, culottes were associated with the aristocracy.

[Harmless Teddy Bear]

He is also credited with making black and white and understatement the masculine ideal for formal wear. He introduced the idea of washing and changing your underwear daily.

For the later he should be made a saint or at least have a holiday in his honor.