Energy conservation. The heat of collapse comes from the gravitational potential energy. If the collapsing cloud was gravitationally bound in the first place--i.e. able to collapse--then there's no way for the collapse to generate enough heat to dissipate the cloud.
Balls don't bounce higher than from where they're dropped.
Doesn't a star that goes nova do exactly that? Forgive my ignorance if this is compeltely wrong.
I think the more intriguing question is why those hydrogen gang members picked the street corners we now find them on to hang out.