I believe it's mostly the latter. I've taken on a management position at work, which keeps me quite busy. It was also part of the reason I was back to work after just taking two weeks of vacation time rather than any kind of formal maternity leave. Two young kids also keeps me a lot busier outside of work than just one baby does.
But if I'm being honest, it was more of a priority as well. If I worked a long day and couldn't make it to the gym, I would go in the evening. I simply don't have the energy or drive to do that anymore.
My solution is to go each day on the weekend. If I can make it both Saturday and Sunday at some point, I only have to try and fit in two gym sessions during the week. So I now have a sitter lined up for an hour or two each Saturday and Sunday.