I'm not sure it can do anything that ARM and x86 can't. But the relevance is that it provides competition to both of those, and competition is good because it keeps things moving forward. And diversity and choice are (mostly) Good Things.
It's unclear. Diversity helps innovation, but it also adds complexity to everyone who builds on top of it. If there's room for significant innovation, it can be worth the complexity. But if there isn't, and there are many signs that there's not much left to do in the traditional general-purpose ISA space, then we're just living with a bunch of complexity for no benefit.
