When I was in graduate school the chances of getting a tenured position weren't anywhere close to 1 in 3. Where are you getting that number?
Many want to do research in the industry, or in public research labs. Many do a PhD because it opens doors in other careers, such as medicine or education. Some PhDs are hobby projects people do in retirement. Some are side projects for people who want to study something relevant to their main job (those are quite common in social sciences).
Then there are those who actually want a career in the academia. But many of them are not trying seriously, because they restrict their job search to a single city / region / country. The 1 in 3 chance is for those who are flexible enough and committed enough and accept the realities of the academic job market.
It's important to understand that in this context, willingness to relocate means willingness to spend your life outside your home country. Even in a large country like the US, there are often structural reasons why universities are not interested in hiring someone like you when you are in the job market.
For example, maybe a field such as ML starts getting popular. Universities respond by hiring new faculty, who in turn hire new PhD students. Almost a decade later, when those students have graduated and are in the job market, the demand may have stablized. Universities already have a plenty of faculty in that field and have little interest in hiring more.
Which means that if you chose a popular field, your chances of getting hired may be below the average. If you want to stay in the academia, your best bet may be moving to a country that didn't experience a similar hiring frenzy and is now trying to catch up.
Although that person may be lumping in the research professorships and various ass. dean positions.