It's confusing, but it is possible.
You have a hidden score called MMR. Everyone in a division tends to have around the same MMR, although it is possible to be in a division that is a little higher or lower than your MMR (this will affect your LP gains and losses). Bronze V is a little different. There's no bottom. So while Bronze III players might have 900 MMR and Bronze IV might have players with 800 MMR, there is no limit to how low a Bronze V player's MMR is.
When the season begins, there is a soft reset. For everyone below the average, they get their MMR increased. Even after going 7-3, you could still be put in Bronze V if your MMR was incredibly low before the reset.
I see that you've been playing ranked since Season 2. There's probably a lot about the game that you haven't been able to learn because you've been surrounded by a lot of people who are all doing a ton of things wrong too, which makes every game feel pretty random. It's a hard environment to learn in. If you are interested, we can give you some advice on this forum that will help a lot. I'm willing to give you some 1 on 1 assistance to help you get out of Bronze. Let me know if that sounds like something you'd want to try.