Yes correct, depending on device you used. This happen form time to time after putting a fresh image on sd card, since DietPi use the default PiHole install methode (install.sh) and not DietPi own PiHole repository any more.
Installation breaks in the middle, without a message and you are back on cmd line. If this happen, you will notice, there is no pihole web password notification at the end of installaton process.
But no big deal, second installation works.
For me, NanoPi Neo, OrangePi One, Odroid C1 (sometimes).