Why did my Rocket League Sideswipe rank change with the new season?

To ensure balance, there is a soft reset at the start of each season. This keeps similarly skilled players together in the same groups, making everyone's experience more fun and giving everyone new goals to reach. 

As you win Online Matches, you will be promoted to higher Divisions and Ranks during the season. Losing more Online Matches than you win will demote you to lower Divisions and Ranks. For more info on competitive ranks, refer to: What are Rocket League Sideswipe competitive ranks?