[Discussion] How will ethereum thrive if Google, Microsoft or Amazon created their own cryptocurrency using a decentralized network?

Ethereum network is thriving and a lot of its "demand" come from its decentralized network where people can create decentralized apps leveraging ethereum's network.

Q: If in case the big three (Google, Microsoft or Amazon) invested on creating their decentralized network and create their own cryptocurrency – how would it affect ethereum in particular in terms of the demand?

Feel free to share your thoughts and references. Thanks!