Brunel was an excellent marketeer who consistently over-promised and under delivered. He also drove technology forward more than anyone else of his generation.
When Brunel was making the Great Western Railway, he decided to survey the route himself because he felt the existing surveyors were slow, expensive and crap. He did this on horseback. During the process he concluded that the horses he was hiring were slow, expensive and crap, so he started his own horse hire company. Somehow, despite this insanity, we got a railway, and it was good.
Disclaimer: it's twenty years since I read a Brunel biography. I might have some of the details a bit wrong.