It has nothing to do with how one day is divided, it's the calendar.
And later, with the calendar came a simpler version with 100 minutes in an hour, 100 seconds in a minute, and so on (Article XI of the "Décret de la Convention Nationale concernant l'Ere des Français" [1]). It was only official (and mandatory) for a few months, however [2].
Edit: the one with 1M seconds a day was only an earlier draft version that never made it into law.
[1]: http://www.gefrance.com/calrep/decrets.htm (in french)
Also, the weird thing was that, although they decided that an hour is divided in ten "parts", and each one of those in ten, and so one... they gave the name "minute" to the part of the part of the hour (so that 1 hour == 100 minutes), and the same for the second vs the minute.
I wonder how people managed to get a hang of this mess...