My take on it is - every language designer (be they an individual or a company), especially ones with a lot of compiler design experience, when they sit down to make a new language, they basically ask what would you do different if you could start from scratch today?
When Sun made Java they said "what would we improve about C++ if we had the chance?". Separate from the JVM concept, this is what they were thinking when they made the language. Back when Java was new people joked it was C+++. When Microsoft made C# they said "what would we improve about Java if we had the chance?".
Apple basically said "holy FUCK we need to get away from this shitty 80's language, C# does some good stuff, but what would we improve about it if we had the chance?
So in C# you used to have to declare something like this:
Something aThing = new Something();
Then languages started asking themselves "wait, why do we have to say the class name twice? We could just get away with just doing it once"
var aThing = new Something();
Swift says "wait, why do we need semicolons? I mean yeah it used to be that we didn't have great ways of telling lines apart but we've solved that problem now. If there's just the one statement on a line no need for a semicolon. And why do we need to say "new"? We know it's new. The calling of the class name via the constructor tells us that. Get rid of that shit too"
Back when c# introduced "var" I was dead set against it. When Swift dropped semicolons I thought it was reckless. Now that I've been using Swift a while I get their minimalist religion. It's a struggle to go back to C# or JS and have to remember semicolons (although JS doesn't seem to give a shit either way)
To declare a constant in C# you declare its type as well as use a keyword
In Swift, they said "well, we're already using var, why not just swap that out for a constant?"
and the compiler in Xcode now shows you all the times when you could use a constant, which is way more often than you realize.
For all the spitballing about platform this and proprietary that, underneath it all Swift is the latest attempt at a language that uses what we've learned from previous languages. And it's possible some or all of their conventions have been used by other recent languages that just got an eyeroll from working developers but Swift has this tremendous advantage in that it has a compelling use case: iOS developers who don't want to use Objective-C. Because no one really wants to use Objective-C. Anyone who says they do is a victim of Stockholm Syndrome.