According to http://www.guidetojapanese.org/surunaru.html:
Since potential verbs describe a state of feasibility rather than an action [...] it is [sic] often used in conjunction with 「~ようになる」 to describe a change in manner to a state of feasibility [...]
(1) 日本に来て、寿司が食べられるようになった。 - After coming to Japan, I became able to eat sushi.
(2) 一年間練習したから、ピアノが弾けるようになった。 - Because I practiced for one year, I became able to play the piano.
(3) 地下に入って、富士山が見えなくなった。 - After going underground, Fuji-san became not visible.
Why does sentence (3) not use ようになる? What is the difference with the other two cases?