Fireball7d7Sandbagging is bad, but moving up teams to a higher division and then having them die is also bad.
I think these move-ups have less to do with sandbagging (there arent any sandbag teams in adv and main has like a couple, and one of which didn't even get moved up lol) and way more to do with the decrepit state of adv. The div has had a low team count for a while but this time it was just not enough teams to adequately run the division.
Theres a couple of reasons for why adv is so dead starting with just how circlejerky the div is. In advanced youre reaching a level of tf2 where teams need more cohesion than any div below. Making a brand new team is just so risky because if the team has too many problems then it just will not be fun and youre locked in for 3 whole months of prison. The work needed to make a team "work" and the risk of playing with new people puts most people off of making new teams so everyone just falls back on circlejerk teams that already know how to play with each other.
Next is just the time commitment. 3 months + preseason is a pretty huge commitment and not everyone has the time. Notice the trend as well of how many people choose to offclass in main on a no scrim team instead of play advanced. are they sandbagging? kind of. but are they going the only route that they have time to play the game? also yes.
as far as solution go i think there are two things that will help a lot. First is just combining IM, Main, and Adv into 2 divisions. Low main can become high-IM, and mid-main and up will have to play against all of advanced unfortunately but those advanced players deserve to play in a division with teams.
Next i think the endless march of season after season should get interrupted. Swapping out a full season for a cup or tournament will have a ton of benefits. Far more people will be willing to play and be willing to make teams when its just a week long commitment or maybe a month if you count pre-cup scrims. Teams that would have played a full season will still be able to participate and can just grind scrims as usual, unaffected outside of not having consistent matches. Plus the relative lull will get people excited to play full seasons and ease burnout so the seasons that do happen have healthier team counts, and maybe even new non-circlejerk teams that decide to stick together.
Basically the monotony and grind of season after season combined with the circlejerkiness of higher-div tf2 means this problem is only going to get worse. It might be too late to restructure stuff this season but i do think going forward some kind of structural change is needed to keep the league healthy and fresh