The Habsburgs were lucky as it was in their inheritances from their marriages. Yet at the same time, they were following a strategy of strategic marriage for alliance and potential inheritance purposes for generation after generation, so some fraction of their OTL success might have been not unlikely.
However, expensive as it was to maintain, I'd think the Habsburgs routine winning of Imperial elections generation after generation probably made them more attractive partners for other dynasties.
Do you agree or disagree with that?