Does anybody know about insulation?

[lowriderdog37]

I just moved into my new house about a month ago here in FL to find that there is almost no insulation in the attic. With the thermostat set at 77 and the temps outside at 90ish, the AC would run ALL DAY! One day the power went out for about an hour and a half, and the temp inside went from 77 to 83 when it was 87 outside.

I decided then that I was going to blast some more insulation in the attic.

This morning, it's finally starting to cool off here, it's 66, but the temp inside the house is still 77...WTF? I opened all the windows to let the house cool off before I go to work. The house is so quick to heat up but won't cool off. The AC seems to be running well, cool air blows out of the vents, and I patched any holes in the ducting in the attic. What would cause this?