They also have some sort of a parallel VLIW CPU architecture that they've been trying to get off the ground for a while now called TILE/TILE64 so that might also play into things.
However since NVIDIA opened their offices in Israel a while ago they might simply be looking for an acquihire since Mellanox is a fabless semi chip maker it kinda fits that also.
Mellanox has driven IB speeds for more than a decade, limited only by PCIe bandwidth. Since they've had NICs that do both IB and Ethernet, they've been driving the ethernet market as well. We've been using their 100G adapters since 2015 (when they were first to market by a big margin). Even today, there are only a handful of vendors that can deliver a 100g NIC. I worry that if Mellanox stops driving port speed, we'll see a slower increase in the speed of NICs due to the lack of competition (eg, 400g will take longer..).
IB still has lower latency than Ethernet at least on paper especially when it comes to RDMA but I don't know how much of an issue that is for these applications.
But overall I'm not sure how much it matters to Mellanox since they are also the ones who are making the high speed Ethernet switches and host adapters.
You also need to use their cables and transceivers (or a similar alternative) for these speeds doesn’t matter if you are using Ethernet or IB.
I had a TileGX dev board and ported our product at the time (nearly 10 years ago). It was an ok arch but that’s a tough niche to fight for.