TL;DR: You trade off exploiting what you know against exploring for better maxima in data. Explore is longer term, Exploit is short term. Older people are likely to exploit beause they'll die soon, just as you stick with what you know / already think in restaurants when you're due to leave a city.

Conclusion he infers is that "it could be" that young people are naive and want more data to understand the world (explore), and older people have more data points and wiser choices (though not necessarily correct), and... so, er... experimentation can be a bad investment. It's a little unclear if he thinks Brexit was a good idea, only because older people had apparently more data points If he does, this does beg a lot of questions as to whether these were rationally-considered data, or even consciously processed.

I'm unclear what conclusion or information he wishes to impart abotu Brexit: that part seems very guess-like and vague.