Yes, but that was the 1970s. Doesn't seem like long ago, but the world has shrunk significantly since then (figuratively speaking of course).
Tasmania indeed has some of the largest remaining expanses of intact temperate wilderness on earth and some parts of it are still quite remote and inaccessible, but I'd note that a lot of this is concentrated in the harsh and wild
south-west of the island which was generally avoided by thylacines in historic times. Even if they did inhabit this area, it stands to reason that there'd be
some quantifiable evidence of their continued existence by this point besides anecdotal roadside encounters and pademelon rump pics. The likelihood of an animal like that avoiding detection for this long, especially with modern technology like camera traps and eDNA, is so astronomically small that it might as well be considered impossible. It's a tough pill to swallow (I was obsessed with thylacines when I was younger, and still am to a degree), but it's better to accept it and use the thylacine's tragic story as motivation for saving other animals from the same fate rather than wasting money on countless "expeditions" that are doomed to fail.
Wait, we're supposed to be talking about the disproportionate number of mammals in PZ, right? Didn't mean to get this depressing