Weights for triathletes / running

[Claybury]

Strange query but - I had to give up a weekly weights session with a personal trainer ( after 3 years ) and have found that my running has started to dramatically improve. I have taken almost 3 minutes off my 10k time which I delighted about but I don't really understand why.
Not much else about my training regime has changed.
Has anyone ever found weight training has improved their performance in races?

[RunnerOnTheRun]

It's simply because you're lighter now as you have lost the muscle you used to have. Cardio eats muscle!