Blackbird nesting habits?

Hello, it’s been a long time since I’ve posted but I’m back. 
There are a nesting pair of blackbirds in my garden (male born last year) and they built a nest in my large conifer tree. However, they just seemed to stop going to the nest completely, abandoning it completely. Now they’re building a new nest in a bush right next to the bird feeder but the issue is she’s chasing after all the birds on the feeder. 2 questions: 1. Why would they abandon their nest so easily when it was fine? 2. Can I move the bird feeder away or would this disrupt her? 
Thanks