SQLite is not a fad. It’s just that it never gained so much attention here before.
I suspect popularity here comes in waves through a Katamari Damacy effect. People start reading about a topic, and start posting, thus more people read, research, post, etc... until a saturation point, a cooling off period, and then a rebuild.
[0]: obviously not the same as whats happening on HN, I'd love to see someone pull these numbers from the HN API!