Why is he resigning from congress also?
Pure Speculation
If he does has an alcohol problem then he probably needs to get out of Dodge as the pressure on his speakership got him drinking more. Once you give up the reigns of power who knows what stories are going to come out. Best to get into a nice recovery center while the storm passes then into a posh lobbying job - time to make his money.
Once again just speculating on to why he’d give it all up
To spend more time with his family. He was told to by the donors
Speakers who step down almost always resign from Congress as well. Hard to be a rank-and-file member after being Speaker and be fair to the new leadership. And probably no fun.
Why is he resigning from congress also?
The office of the Speaker is the only one big enough for a tanning bed.