I think people raised some very good points in this thread, although I just want to make clear such a tactic is by no means cheating. There are many situations in BuzzerBeater where you have to choose between long or short term success. In some situations you choose to sacrifice some short term succes in order to gain more long term succes and visa versa, for example selling a starplayer to invest in awesome rookies, or buyin your new Lebron instead of expanding your arena.
As maleshka already pointed out in
(144528.10), this manager probably, unfortunately, decided to quit the game and therefore sold his whole roster.
But let's say he really choose to do what the original poster suggest he did; sacrificing tons of short term succes in order to be able to bounce back in the long term. I really doubt the effectiveness of such a tactic. As Steve Karenn already pointed out, in many divisions you are not guaranteed to promote back straight away with a new roster. Relegation is disastrous for your economy, and quite some people underestimate the (financial) effects of being relegated.
Let's say you apply this tactic in the top division which earns your an extra $500k/wk, this is about 7M per season. In most top divisions you can buy just 1 new starter for your team, I'm not sure if that's worth relegating.