Toilet supply line seems connected somehow that I can't see, what do I do?

I’ve just bought a bidet and assumed that replacing the water supply line would be easy, this is turning out to be a bad assumption. After unscrewing both sides neither side seems to come out, I’ve tried pulling on both sides and the top will come down a bit but it feels like it’s under heavy tension and as soon as I let go it’s pulled back into position as if something is holding it in place. The bottom side doesn’t move at all and it feels like pulling on it that I’m just going to rip the valve out of the wall.

Do I just need to pull harder or is it possible that the top is somehow connected to something inside the toilet? Certainly this isn’t some valve/line/toilet package that isn’t meant to be separated?