Why the love for 912?

As has been said, power vs weight and balance.
Porsche have improved the inherent problem created by hanging a, relatively, heavy engine over the rear wheels by using technological improvements on each iteration of the 911. It now takes an awful lot of idiocy to get a modern 911 to bite and the result is that most people can drive one at 9/10ths with very little skill involved. I used to say that I could throw the keys of my Turbo S to anyone and the car would flatter them and make them look like a driving god. I've said it before but for me the sweet spot between analogue and digital is the 993; however, each persons line in the sand will vary and I know plenty of people who now call the 997 a 'modern classic'. The 993 was the last of the air-cooled and it sounds, to my ears, the way a 911 should sound and drives like a more mature 70s 911 but without the comprehensive safety net of the modern versions.
However, I digress. Your question was 'why the love for the 912'. In short, the balance. They lack the weight of the 911s engine and therefore, when set up properly, can be a very enjoyable classic to drive. I don't think I could own one with the 90bhp engine but the base engine is tuneable, far less expensive to work on than a 911 engine, and at 130bhp+ I'd be more than happy to use one on a regular basis. Iconic shape, fast enough to enjoy on our busy roads and nimble. They hold the same appeal as the Lotus Elise and other cars that rely on lightness rather than outright power as the route to enjoyable motoring.