Why Samsung hit a wall

“Samsung’s smartphone ascent was breathtaking,” writes Asmyco’s Horace Dediu in the post that accompanies this chart. “From having essentially zero market share in the category in late 2010 to becoming the largest vendor took less than two years.”

Dediu writes in the past tense because Samsung smartphone business hit a wall in quarterly results reported Thursday. Sales growth slowed and profits collapsed — down 74% year over year — while the rest of the smartphone market barreled ahead.

What happened? According to Dediu, the market hit a fork in the road, bifurcating into an “upper” market with integrated offerings (Apple and Xiaomi) and a “lower” market populated with hundreds of vendors and thousands of products at every price point.

Samsung is stuck in between, trying to sell middle-of-the-road smartphones at high-end prices.

Management sees its strength is as a fast follower that can deliver in volume. But without its own app store, its own ecosystem, its own software and services to differentiate itself from low-end distruptors, Samsung was always at risk of being overtaken.

“At some point,” says Dediu, “the fast follower exposes themselves to being faster followed. Better to find new lands to conquer.”

Below: Seven years of smarphone shipments.

Smartphone ships

Chart: Asmyco. Click to enlarge.

Asymco link: Faster followed.

See also: Samsung’s ugly third quarter: What the analysts are saying.

Follow Philip Elmer-DeWitt on Twitter at @philiped. Read his Apple (AAPL) coverage at fortune.com/ped or subscribe via his RSS feed.