"Bad luck" is the common thing here when attacking.

right now: lost a 7x1 down to 1x1 (4 3x1, plus a 2x1 straight)
then moved to lose a 9x7 down to 3x3 (lost 2, won 2 won 2, lost 2 lost 2)
then moved to 16x13, down to 5x0 (won, but still, lost more than the "average")
then moved to a 9x10, down to ...

Probabilities of winning a dice roll in Risk
(various die combinations) Attacker
one die two dice three dice
Defender one
die Attacker wins 41.67% 57.87% 65.97%
Defender wins 58.33% 42.13% 34.03%
two
dice Attacker wins 25.46% 22.76% 37.17%
Defender wins 74.54% 44.83% 29.26%
Both win one n/a ...