Take away the payroll vote of 140, and this means Theresa May had the backing of around 50 Tory backbenchers on the central policy of her government.
Surely the 'central policy' as per the Conservative manifesto is that we will leave the EU. The compromise Mrs May was putting forward would not have got us out, so voting against it was the correct thing to do.
The size of the majority would have been because Brexiteers would vote against it as it is 'BRINO' (Brexit in name only), while Remainers would have voted against it as they do not want Brexit in any form.

All the pundits were projecting that Mrs May would lose. It was only the size of the loss that was surprising.