If Russia picked a fight, why was Georgia making progress at the start of the war?

I mean, if Russia would pick a fight with Finland. The Finns, for all their resilience, would not capture St. Petersburg at day one of hostilities.
The Georgians did in fact, capture the hostile capital of South Ossetia. I would label suprise as the only way they could have achieved this.
If they suprised Russia than it was not Russia picking a fight there.

Sakashvilis gamble did not pay off, and now he is trying to win via the media what he could not win via his military.