Because we are hell-bent focused on making sure your display campaigns are awesome.
Oh and also because we think our smiley, optimistic personalities provide a great contrast with the image of ‘hell’, and also the straight parallel lines of the double-l in ‘hell’ provide a great contrast with the ‘bend’ imagery of ‘bent.’
For non-native English speakers, ‘hellbent’ is an informal word, probably old-school slang, that means obsessively focused on something: literally, you are willing to bend hell itself to make it happen.