That just depends on what you mean by 'smart'. Plenty of people are intelligent, competent, have great ability at something, but lack the wisdom to recognise their limits.
It is indeed arrogance, but it is absolutely common in smart people. At least for some kinds of smarts.
Re:Tesla Q1 2020 Update
by renewiltord on Wednesday April 29, 2020 @08:40PM
(#23026292)
Lots of average people tell us what "truly smart people" are like. No one actually knows.
Truly smart people know that their abilities and success are fleeting and do not extend beyond their own little sphere. And if they do venture beyond they are humble and learn from the wisdom of experts. They never, ever think they are good at everything.