'Responsibly' is a pretty subjective term in the context of Uber. If Kalanick had been running Uber by any conventional definition of 'responsibly', it would be a fraction the size it is today.
And it's still nowhere close to what I imagine Kalanick imagines. Short sighted investors will see Lyft, Ola, Grab, Didi as competitors. Kalanick will see private car ownership as competition. I have a feeling if he doesn't come back, Uber in it's current form is the best of it we will see. If Benchmark would have had 20% control over Facebook, it would be the best social network colleges ever had. Nothing more.