Honestly though, I think the impeachment just pointed out the Ukraine stuff about as much as it pointed out Trump's phone call shenanigans, it wasn't good for them politically to keep at it, his approval rating was going up and he was raising tons of money during it. It was backfiring politically for them, the majority of the public wasn't interested (especially after the Russia thing coming up empty, you can only cry wolf so many times) and it brought their own misdealing to light so they didn't push it as they would if they really cared.
Honestly though, I think the impeachment just pointed out the Ukraine stuff about as much as it pointed out Trump's phone call shenanigans, it wasn't good for them politically to keep at it, his approval rating was going up and he was raising tons of money during it. It was backfiring politically for them, the majority of the public wasn't interested (especially after the Russia thing coming up empty, you can only cry wolf so many times) and it brought their own misdealing to light so they didn't push it as they would if they really cared.