A high speed (78rpm) was initially needed to hide the distortions inherent in early recording and play-back equipment.
As such equipment improved, lower speeds were possible. 45rpm offered good sound quality but only limited recording time (or around 3 minutes per side on 7" records).
That was of little use for classical music (where at least one movement of a symphony needed to be fitted onto a single side of a disk) so larger disks, with a slower speed (33rpm) were used. (It was only later that such disks were used for 'albums').
However please don't ask me why those precise speeds were chosen (rather than, say 80rpm, 50rpm and 35rpm). I've often wondered about that myself and I've yet to find a clear answer!