It depends on why I admired the people. If I admired them for their success in business, then yes, I would expect their writing to show attention to details like spelling. But if I admired them for something else, I wouldn't necessarily expect that. I'm certainly not saying that anyone who is worth admiring has to spell correctly.
If you think this way, it's worth going back and examining the writings of people you admired. You might be surprised! Or not.