Well, first you start out with an IQ of say 140+, then you matriculate at a first tier university, and major in Physics, or Mathematics, or Astronomy, and after four years of hard work you get your Bachelor's degree; then you apply to grad school and get into an Astronomy/Astrophysics program, and after a couple more years of hard work, you'll have your Master's degree, and then you put in more time doing original research on your doctoral Thesis, which, with a bit of luck and a lot of hard work, might be accepted, and so you eventually get your Ph.D.
Then you go to work, continuing to do original research like these guys did, and by that time you would have come to understand how it is that scientists are able to devise observations that measure the age of the Universe using multiple independent methods, which indicate very similar results.
Hmmmm...then why is it that, every so often (yearly or more, it seems), the processes yielding "similar results" change by a few billion years?
In my under 40 lifetime, the state-of-the-art guesses of the universe's age have varied by several fold.