alt Hacker NewsSorry, but you're incorrect.
If a particular product is tied to a specific proprietary tech stack, then the consumer is also tied to specific suppliers. This is known as vendor lock in.
Microsoft used this approach with Internet Explorer back in the old days; ensuring that it provided proprietary elements and implementation, that would encourage developers to provide websites that only functioned using their browser.
Open standards allow choice.
That can be one aspect of it, though I would argue that doesn't mean open standards are always better for competition.
I think you're also assuming the only competition that matters is long term. In the short term the potential for locking users into your own ecosystem can incentivize short term competition.
Long term competition seems like a good goal, but that assumption wasn't part of it at the beginning of this chain.