I've read up on it a bit and I think I understand the basics. The 3-month debt ceiling extension gives the Democrats key negotiating leverage in December when the debt ceiling is up for discussion again. A 6 month or longer extension would have given the Republicans more power to pass the legislation they want over the next few months.
What I don't understand:
Bills are written in the House and sent to the Senate and the Republicans still have the majority. Couldn't they just use their majority to write any bill they wanted and send it to the Senate? All they need is 50% so they can pass anything they want, unless the tea party dissents, which has happened before. They can write their own bill, send it to the Senate and if it passes there, to Trump, challenging anyone to vote down the bill, which would be a vote against Harvey relief and a vote to shut down the government. I don't understand why the House can't just pass whatever they want and why Trump saying "I'm going with Nancy and Chuck" made this a done deal. Agreements are often reached between the President and Congress to make a compromise, but I've never seen one reached between the President and the minority party before, and the minority party can't write and pass bills, though I suppose with the President's stamp of approval, this one passed.
If anyone whats to chime in on "what was Trump thinking", I welcome that too, though I realize the "what was he thinking" is opinion, but at the same time, you can work out a person's strategy, so it's not entirely opinion. I think Trump wants to revisit the Wall as soon as possible and that's a key issue for him, that's why he was fine with just a 3-month spending extension. I also think he wanted to hit Paul Ryan sharply in the nose with a rolled up newspaper and this was his way of doing that because they've clearly had quite a bit of conflict recently.
How a president and a minority party can make an agreement and make it so. Has this happened before?