Personal grudges. Academia is full of them.
If some in your experience erred on the side of leniency, then it stands to reason that others might err just as egregiously in the opposite direction.
In fact, your anecdote suggests erring is the norm. We should thus expect punishments to be inappropriate in one direction or another. An appropriate punishment seems rather unlikely.
Universities and other similar large institutions usually err systematically in one direction - that which protects the institution.
No respect for the plagiarist physicist, but an easy way to control what media representatives of scientific disciplines get to say publically, is to start out with what amounts to "academic compromat" (scientific fraud, plagiarism, ...).
Did this physicist / media star recently say something controversial?
I mean why did the system let him pass as a physicist, and why did it let him rise the media rank?
Not really. This is the consequence of an investigation by some journalists about a decade ago, and an audit that lasted for almost 2 years.
> I mean why did the system let him pass as a physicist, and why did it let him rise the media rank?
He is a smooth talker and by all accounts good at vulgarisation. He does well in interviews and is easy to deal with for journalists. There’s always been controversies but media thrive on those.
With another professor I caught a flagrant case in a student thesis and we faced attacks from the university administration because the student had a stellar transcript (also not the positive signal some might think). Punishment was almost inexistent.
It's difficult for me to imagine what it would take to get a doctoral thesis revoked.