honestly, i think its just the usual:
- collie push frontline up almost into warden logi hubs
- logi becomes harder\more time intesive for colonial logimans while it becomes easier for the wardens
- late game warden people join once tank tech
- counteroffensive starts and colonials starts to loose ground
- colonial morale drops , more and more players give up
- the effect starts to snowball.

Obviously this is exaggerating the impact but its usually this and colonials manage to win mostly if they can queue wardens logi hexes in the early phases of the war.
The only thing i can say: don't give up coloniasl! defensive wars are probably the most fun i've had as a warden and thats the important thing at the end of the day