For a long write up with more data and some reasons for it:
https://bsky.app/profile/did:plc:ql4ykel4bgsqzslwsa3lflh2/post/3lcdewkbmf22w
Keep in mind Russia is a massive country and trains are amazing at transporting freight over long distances. So they have a lot of regions and industries depending on the railroad. Much more so then in most other countries. Some places can hardly be reached by road, but can be reached on train.
It looks like they average the daily load for each month. There is only one data point per month. So each January has a lower average daily load than the previous December. The data isn’t continuous but the lines connecting the points make it seem like it is. It’s a poor graphic and should use dots or bars for each data point to be more clear.