For the House Democrats, a fruitless impeachment is likely to be a political fiasco and dead weight in the 2020 election. Pelosi knows that, but many in her caucus are already invested in the effort.
Exactly. Funds are authorized to be reutilized under certain POTUS determined circumstances. Getting a court to do something about it (the law) is less politically risky than impeachment and no conviction... The sentient Dems know this.