MOST countries' kings practiced "Diplomacy by marriage." Austria stood out by making it work. That's because her kings' marriages seemed to be highly topical, rather than random.
For instance, there didn't seem to be much of a point for Maximilian of Austria to marry Marie of Burgundy. Until you realize that Austria is on the southeast edge, and Burgundy/Netherlands was on the northwest edge of the Holy Roman Empire, and Maximilian was likely to (and became) Holy Roman Emperor.
The marriage of Maximilian and Marie's son Philip to Ferdinand and Isabella's daughter Juana didn't seem to make much sense either, until you realize that Spain and the Netherlands were on the south and north of their common enemy, a newly united France.
A couple generations later, the marriage of Austria's Prince Ferdinand to the heiress of Bohemia didn't seem to have to particular meaning, until one realizes that it enabled Austria, Bohemia, and the Holy Roman Empire to split off from Spain and the Netherlands (the latter two under Philip II).
On the other hand, the marriage of Philip II of Spain to England's Queen Mary didn't do much for either, except to arouse antagonisms on both sides. And the marriages of various French kings to Polish princesses didn't do much for France, because Poland was a liability, rather than an asset to France, given all her enemies. The marriages of French Louis (XIII and XIV) to Spanish princesses didn't reconcile these natural enemies.