TL;DR: The order in which you expand from your niche matters. Each adjacent market should leverage your existing advantages—distribution, brand, technical moat. Amazon books → media → everything is the canonical example.
Most startups either get stuck in their niche or expand randomly into unrelated markets. Neither works. The right sequence is one where each step is defensible with your current strengths.
Sequencing markets correctly is underrated. It’s the difference between momentum and thrashing. Pick your first market ruthlessly, dominate it, then identify the adjacent market where you have the smallest unfair advantage but it’s still yours. That’s your next target. (zero-to-one, monopoly-vs-competition, power-progression)