Disappointing, and really surprising so many are involved. I'd be disappointed, but less surprised, to find out there was one or two bad apples, as there are in every profession. But 100? That's shocking!
What's also odd is the article states the people involved were mostly teaching on contracts, not full time professors. I'm surprised they are even allowed to take on a Ph.D. student. That's certainly something quite different from the US universities I've worked at where you need to be tenure-track and voted in as a member of the graduate faculty in order to be allowed to supervise a student (mostly, this is done for stability to ensure that students don't end up suddenly without a mentor when someone's contract isn't renewed).
Do they also not have dissertation committees? Again, the US system, and I think the Canadian system as well, require students have a dissertation committee, not just one supervisor. I don't know if official committees exist in other countries, but I do know they at least ask for impartial "readers" for the dissertations from outside their own institutions. All of this is again done so there isn't just one person making the decision whether a student is ready to graduate with a Ph.D. It's supposed to both protect the student from a mentor who might delay their graduation for selfish reasons of keeping a good student doing more work for them longer, as well as to protect the faculty member when a student isn't cut out for the degree and it's more than one person "ruining the life" of the student. But, it's also supposed to help avoid impropriety like this, because it's not just one person you need to please with your work, but a committee of several, anyone of whom can intervene and say you are not ready yet.
I guess the real question then arises...did these students demonstrate sufficient competence to earn their degree? Clearly there was motivation of their primary mentor to push them through and get them to graduate whether earned or not, but were the other checks and balances in place to ensure these students did manage to earn their degree, in spite of the impropriety of their professor?
If the students weren't aware of the bribes (i.e., they thought they were paying to get help with the application process only), and really did do the work they needed to do to earn their degree, I'd feel very sorry for them to now have their credentials tainted by this.
The other question is how did it go on so long without getting reported sooner? How many others turned down the bribes, but remained complicit by not reporting the offer?