Thee tories knew that their votership of pension age that has been their 'reliable' voter is rapidly dying off, and once the pensioner is not big enough to make a huge difference in their voter tally books, bang goes the triple lock and bang goes every other little incentive they've given them.
The tories are happy because Labour were the party that was going to fall on, so the last memory of the benefits the tories give them because Labour took one away, will be of the party that implemented it, and it wasnt going to be them.
tl:rd Tories would have done the same thing sooner or later.