I bred tropical fish for about 8 years before getting into snakes. Once I had a couple of snakes the fish went forever and I never looked back. I still like fish a lot, but I like reptiles so much more and they're just so much nicer to work with. If fish were as low maintenance as reptiles I'd still have a few, but all those water changes, the frequent feeding, keeping an eye on water chemistry, the greater potential for things to go wrong, the occasional broken glass and flooding and the constant risk of it, there were just so many more hassles involved. I can see the appeal of having a fish tank in the lounge room as opposed to a snake, they are more active and fun for visitors to watch, but if you want more than a very small number, reptiles are just so much nicer to manage.
If people are switching back maybe for some it is because snakes in Australia are moving from 'oh my god, what a bizarre pet, I've never even seen one up close, that's the most incredible thing I've heard of' to 'oh yeah, heaps of people keep them now'. I do still meet a surprising number of people in Australia who think of snakes as amazing and mysterious creatures who the concept of pet snakes is still mind blowing to. Much more in Melbourne than further north.