Apart from Facebooks try with Libra, is there anyway they could start competing on the blockchain world? My take is that they should.
No, because their crypto currencies would be centralized ones. They couldn't compete with bitcoin, ethereum and so many other decentralized altcoins.
Libra (now called Diem) is a good example of how this competition isn't going to happen. It will be a stable coin like many others which already exist and are even more trustful in my opinion, moreover investors are looking for speculative crypto currencies which they can make profit by holding and trading. It's not the case of these big corporations' crypto currencies.
Actually if I wanted to associate myself to any of these corporations you mentioned I would buy their stocks rather than their crypto currencies.