I know this is a very basic question, but what is it about algebraic effects that makes them compose when monad transformers don’t? I’ve read some of Bauer’s e

I know this is a very basic question, but what is it about algebraic effects that makes them compose when monad transformers don’t? I’ve read some of Bauer’s early Eff work, which IIUC was explicitly motivated by this, but for all the neat stuff about resumable exceptions and delimited control and whatnot I don’t feel I ever saw (or recognized) the definitive answer to this.