Underestimating compounding and secondary effects, especially while rationalizing the abandonment of their core market and capability is one of the most famous ways that big companies provide evidence of their downward spiral. I can feel the MBA energy from here.

Can you name any companies that suffered by switching focus away from one market where they dominate in order to also dominate a market that is 10x the size of the first market already, and growing faster?

If switching focus goes along with 'underestimating effects of ignoring core market and the treating competencies in it which lead to the market domination in other segments as legacy of the past which should be abandoned', then take your pick. A few off the top of my head: GE, Sony, HP, RCA, IBM.

Every specific situation is different, but the pattern I mentioned is easy to find. Here are three examples: RCA, GE, HP.

CUDA is where it is today because some years ago, people in grad school screwed around with CUDA on their personal gaming PCs