Fish, birds, animals and plants interested me way back when I was a young child. I would see birds in the wild flying about and when I saw a nest or eggs, I was in heaven. I remember being in a school outing as a 6 or 7 year old and we went to some animal park. They had aviaries there and I spent half the day sitting in front of one with a female quail that was sitting on these tiny blue eggs. When I was at the beach or out fishing with dad, I would spend most of the time looking at fish and other things in the water.
When I got my first tank I had a few goldfish. My two younger sisters got small tanks as well but they didn't stay in fish so I inherited their tanks.
After keeping goldfish, I went onto tropical fish and then wanted saltwater. I tired marine in a small tank and failed, so got a bigger tank and failed. Bought a book on marine fish and found out about the filter cycle and worked out how to keep marine fish.
After my first success with marines I found rainbowfish and got into them. I started breeding them and needed more tanks for the different species. I also got into cichlids, catfish and unusual tetras & barbs, as well as temperate natives. Each species got its own tank or was mixed with others in the case of rainbowfish.
Within 10 years I had gone from 1 tank to over 40, and I was working in a pet shop too, so saw more fish I wanted and kept them all
The same thing happened with birds (MBS) when I was keeping them, and gardening (MPS). In my garden before 2016, I had several thousand plants in pots and more in the ground, mostly natives and a number of them were rare or endangered. The endangered plants are now presumed extinct thanks to mine being thrown out while I was homeless.
It happens in lots of hobbies, you start off with one and then see something else you like so you get it. Over time (if you stay in the hobby long enough) you develop multiple whatever the hobby is syndrome, be it cars, bikes, birds, fish, plants or any other animal. And when you lose it all a part of you dies.