Aside from meaning 'hat' it is also used when giving someone respect, a short way of saying 'hat off' or 'I'm so impressed, I take my hat off'.
Chapeau! Something I'd never be able to do even with training!
but chapeau! "by adding an Exclamation mark" is usually used to express appreciation, admiration, approval or respect
It's like when you say:
Kudos! I take my hat off to you! Well done! Hats off! or My hat's off to you
person 2 : chapeau! I'm speechless.