Why do some PhD programs recruit only a handful of students and other recruit more than 100?
The reliability of a program depends on many things as does the number of slots available in a given year. I have no reason to doubt that the University of Lisboa is anything but reputable.
But, if they are willing to admit up to 110 students in a given year it doesn't necessarily mean that they will. They will apply some standards to every application and might fall short of the goal. The goal might change from year to year depending on graduation and drop-out rates. It might be half the next year, though unlikely.
But the reliability depends on the rate of graduation and where the graduates wind up and not on the absolute size of the program. In fact, there may be many specialties within such a faculty, so it may not seem so large to any particular student.
But a given faculty member can probably handle three or four (more?) doctoral students at a time if they are in different stages of their programs. Some can handle many more, depending on the organization.
Look to other factors.
I was in a large program, though not quite that big. Things have gotten bigger since that time, also. But the research seminar I was in had about three faculty members and half a dozen students. Graduate classes had about 30 students, and the entire graduate student population was spread over many courses. It can work and still have high quality. In fact there can be a certain synergy that comes with a large faculty.