It's reminiscent of the endgame at HP, where the formerly profitable PC/printer division has been split off from Enterprise - possibly in an attempt to keep at least one afloat.
That's not proof of badness, but it does suggest desperation and lack of imagination.
It's completely different. Yahoo is not splitting up its core businesses.
They're taking a non-core asset (the Alibaba stake) that they can't sell without incurring a huge tax bill, and separating it from yahoo Core so that they can hand it over to Yahoo's shareholders (presumably in the hope that someone else - e.g. Alibaba - will step up to acquire it, thus unlocking the value for the shareholders), and re-focus on Yahoo's core businesses again.
There is a separate issue that the core of Yahoo is performing poorly, and that fact may well result in Yahoo Core being split up and sold off but it's important now to conflate the two issues.
That's not proof of badness, but it does suggest desperation and lack of imagination.