As an ex-member of a team who used react, redux, typescript, observables, epics, thunks, custom hoome-grown validation libraries, websockets and elixir deployed in two different microservices to build a... signup wizard... I can confirm this.

I proposed to build it in Rails (which we already had, but was the "old monolith we're migrating away from") and I almost get crucified.

That's a story I'm familiar with, but I am not actually aware of any (major, commonly used) tools that were created out of boredom. I only see instances of people using existing tools when they are not necessary out of boredom.