Hitler personally disliked Fraktur and gave a speech against it in 1934. It continued to be used as ‘the true German script’ until 1941, when the party did a 180 and banned it under the pretext that it wasn't Fraktur, but Schwabacher, a similar blackletter script, which they called ‘Jewish letters’.
Moreover, it was banned so hard that cursive scripts Kurrent and Sütterlin were forbidden as well. As a result, people educated after 1941 often couldn't read handwritten letters and notes of their ancestors.