To start, we don't balance our ranked distribution based on what League is doing or their system. While I do talk with their designers, the Valorant team believes in the decisions from my team to do what we believe is the correct distribution for Valorant.
There are two outcomes I'd like to hit when setting our ranked distribution:
1.The community can start to paint a picture of skill related to that rank; "That was a Gold play", "That player has the crosshair placement of a Bronze player", etc.
2.Climbing ranks feels like you've increased in skill to get there, and by getting better at the game that rank increase feels meaningful. This prestige can also be seen in the population % of each rank, especially at the high ranks.
So with the above goals in mind you have to decide on 1 of 2 ways to balance your distribution:
1.You balance based on MMR, so every rank is even. For example; Iron = 500, Bronze = 600, Silver = 700, Gold = 800, etc. Because you use 100 MMR between each rank, that means a silver playing against a bronze player would be the same skill difference of a gold playing a silver. This makes it so as you climb you feel like each rank has a similar amount of skill difference to them.
2.You balance based on populations %'s and wanting each rank to have a certain amount of players in each rank.
Personally, I'm a bigger fan of balancing based on population than on a static MMR number that's the same for all ranks. You could actually get pretty close to the population %'s you want for each rank if you did a static MMR system and worked out the math. But again, I'm a bigger fan of balancing based on population %.
The reason I like balancing on population % is that I think it's easier to digest than MMR, especially if your MMR system is not forward-facing(like ours). How are players talking about our system? When I talk about my rank I often like to say "I'm in the top x% of players when I'm Diamond", and I know others who do the same. So we balance the system how players talk and think about it. There are some other reasons, but I'm dragging this on a little too long.
Now, why is Silver the center point? Silver "feels" like the center point of most ranked systems. When I've played games in the past Gold has always felt like the first step into the higher-skilled player pool and I want to keep that feeling. Silver should feel like "I made it to the middle of the pack" and going above that should feel like climbing above that group. You could also argue that this thought of silver being "Middle of the pack" can be seen in society or other games.
As a designer, I'm very focused on the player experience. Above I called out, when playing other games, I've felt like gold is starting to get into the higher skill pool. This is super important because players coming from other ranked systems often have expectations or ideas of what the ranked distribution should be. So I combine what I believe is best for the community, what players expectations are from playing other games, and we looked at League because it's another Riot game players may be familiar with. Obviously, Gold in league is a very important rank because that's where you get your ranked skin, so it just reinforced my belief that I wanted gold to start to feel "Above the pack".
I also like the higher ranks having a smaller population % because it feels very prestigious to get those ranks. Ranked is about improving your skill and being rewarded for doing so. I haven't been a huge fan of systems where the higher ranks become a hangout spot for a large group of players. You also want to take into account match making pool(so ranks aren't too thin). You also don't want ranks to have too big of MMR spreads, then ranks feel bloated with players of different skill. There are also some data considerations, and other small factors but I think talking about the player experience paints the best picture on why we ended up where we are.
This post brought to you by 1am EvrMoar wanting to answer /u/TimeJustHappens, because they have been such a positive force in the community. Seriously thank you for all you do, I often will get to a post and see you helping players out with questions they have around our systems. This post was written quickly, and I'm sleepy, so sorry for being a little all over the place but I wanted to answer because it's a fun topic!
I hope everyone is having a good first Act of the new Episode. Thank you all so much for making me feel welcomed in the community(I just hit 8 months at Riot!). I'm excited for the next year, and all the future Valorant content we will get to experience together!