I am assuming that the hypothesis of an Indo-European phylogenetic relationship is the best of such kind, within the historical-comparative linguistics. It is the best proven, it has the richest data from a huge collection of languages; nobody ever questions its validity as a whole.
It is exemplary and prototypical both in research and teaching. For example, when a new genetic hypothesis is proposed by someone, the IE hypothesis is often used as a reference for evaluating the quality and the quantity of the new hypothesis. Or, again, when students are taught the basics of the comparative method, the IE examples are always the easiest to quote and also the most convincing.
Partly, this is certainly explainable with some random historical conditions: we are extremely lucky in having thousands of years of written attestations of the IE languages.
What I am asking is this: do you feel like there are also some strictly linguistic reasons for the superiority of the IE hypothesis? E.g., some typological property shared by all the oldest IE languages such that the comparison is made easier, the cognate sets are richer, the phonological correspondences are more regular.
This is a serious question, not a curiosity.