OpenLayers is probably what you're looking for. It supports multiple projections. It's a wonderful library, but a bit more ceremony is required than MapLibre/box and leaflet.
It is funny isn't it? I believe it was the opposite direction mostly though, as you say, "railway... and light"; to solve their own problems of powering their infrastructure to move people, they got into power generation at a time when there weren't as many players doing what they needed to run their primary business. I'm not sure that power generation getting into trains would be as effective. Nor do I think an LLM/AI company getting into chat and discussions would be valuable. It feels wrong. But hey, "happy" to move on to yet another chat program in my life if it's better than what we got...
They didn't, no one asked google to do it. It was Paul Buchheit's 20% project. Google saw a good thing, solved by someone who knew what they were doing and where they wanted it to go, and fostered it. Hell, it is what built AdWords and ultimately made google the advertising behemoth it is today. I don't think this is the same thing...
I see what you are saying though, a business can expand beyond it's initial constraints, but I'm not sure that chasing prospects like what is described in the OP is really all that successful.
This is just crazy. Lets ask the power company to build some trains for us. They transport electricity, they _must_ know about transporting people. They can power the lines themselves!
If this was so easy, teams wouldn't suck, matrix would be everywhere, and discord would be replaced already by the furries (as much as stoat is trying).