For an example, Google has Chromecast/YouTube, Amazon has Amazon Fire/Prime Video, and they're less and less interoperable year upon year. This war creates an edge that Roku can squeeze into, which has support for every major vendor except Apple.
I find myself using Target and Walmart's websites more than ever before, not due to some moralistic protest, but simply because they're now more competitive and have products Amazon don't stock (like Google Home Mini for one example).
I find it interesting from a business perspective that Amazon chooses to push out competition, whereas most major retailers stock both own brand and branded products side by side, and profit no matter what the consumer selects.
I wonder when Alibaba US and EU will open. If Alibaba will sell anything and Amazon is protectionist, I can see that being Alibaba's edge.