Parliament is a bit like a football game:
It's Government versus Opposition, but obviously the Opposition team always has to play with 10 while the Government team plays with 11 - they always have the upper hand.
Currently, in the opposition team, the SNP, Lib Dems, Plaid, Greens, etc. collectively make up 3 of the 10 players. With the game in full flow, they are playing against the Government team as best they can.
All of the other 7 members of the Opposition team have spent the whole game so far in a huddle in the corner, arguing amongst themselves over the captaincy.
Meanwhile, the Government team are playing with 11 men against 3.
Can you see why the Tories are getting away with doing what they are?