Perhaps someone pointed out to him that the 'single payer system' is fought against by all those lobbyists who pay for the Democratic and Republican re-election campaigns?

And he, who has spent lots of money to buy Senators in the past, decided that single payer is just not going to happen?

Senator Ron Wyden, Oregon Democrat, was just re-elected for another 6 years.  He is an eager opponent of  Trump and the Republican Health plans.  

Look where he gets some of his money:

Campaign contributions as of 12/31/2016:

Blue Cross/Blue Shield               $78,400
Da Vita Health Care Partners :  $45,900
Vibra Healthcare                            $34,300

Health Professionals                   $527,848
Insurance                                        $609,907

And our other Democratic Senator Merkley, who doesn't go for re-election until 2020,  has also found the Health Care Gravy Train.  He's just newer at it!

Health Professionals   $188,896


Follow the money!  Then count the votes!