Consider that the PC has historically been purchased by IT departments which led to a monoculture of Windows which led to a persistent leadership for Microsoft.
The music player created dominance around iTunes mostly because the distribution model for music labels was baked-in. With network effects, the iPod quickly gained and perpetually retained market share leadership.
The smartphone business initially favored Symbian and BlackBerry because they had the market access through operators. After the touch UI became dominant (and incumbents failed to respond in a timely manner), Apple and Google took leadership as soon as they accepted the operator distribution model. Android in particular is especially resonant with operators and has been developed with their requirements in mind.
The tablet business is more like the PC business but without enterprise requirements or patterns of purchase. This has meant that app/content ecosystems and retail distribution were the key gating factors. The story is still unfolding but so far Microsoft has not found a foothold while iOS and Android and Amazon have.
That leads to the question of how will smart TVs be sold and which business model (or go-to-market strategy) will succeed.