I'm not saying that philosophy is bad, just that reality is complicated.
"Scrap the project and move on" works in some contexts, not others. The way startups/products actually work, often, is evolutionary. If your texting idea didn't work, but you see a chance to pivot into something... are you really going to just fire everyone and tell investors "sorry?"
That said, the "one thing well" philosophy really does have big engineering advantages. You can't have everything. I'm just raising the "retrospectives" warning.
In any case, the "$1 per year" was never a real business model. They never even got around to actually charging it... because anything that limits the usership of a messaging app will sink it. It's the opposite of "support everything" strategy that made them successful.
"Sell to Zuck" was always the plan.