Question is why do we need a leader we relate to? We're not living in tribes any longer. The president of a country isn't likely to sit down and have a beer with us.
You've turned the question around. I don't think it's particularly important that people relate to their leaders. However, if leaders can't relate to (i.e. understand) the people they lead, then you might end up with misaligned goals and motivation.
For instance, if the president of the country is wealthy and associates almost exclusively with and identifies as a wealthy person, then that person might consider their primary goal as president to promote economic growth as measured by the stock market. Some less well-off constituents might rather the president focused on programs to improve access to food, health care, and education for the less well-off.
This isn't an either-or thing; a president could do both. However, if non-wealthy voters think the president doesn't understand their situation or have any policies in place to improve it, then to that voter is not likely to have a high opinion of that president.
Given the choice between hearing a stranger talk about stuff you don't understand on TV, you'd choose the one you 'like' more. It's that simple really.
Trump is no more a leader to you or me, than Brad Pitt. It's just some person on TV you never come in contact with.
A better question is why is there voting for a president, by people who don't understand anything about what it takes to be good at that job. Absolutely nothing for the vast majority.
Why do developers often wish a manager/superior had technical knowledge? We hope they understand what we're doing and will make decisions with that in mind. We can also accept "hard decisions" as being more carefully considered rather than simply not understanding the situation and costs.
