Earlier quoted context omitted.
How is it a collapse for the Tories when they still have 48.5% of the vote? It seems pretty good to me - though I'm not familiar with English politics. (Serious Q not attacking)
You might have noticed that the last US presidential election was not won by the candidate who had most of the vote. In a similar fashion, the key thing in the UK vote is individual district elections of members of Parliament, not the % of the overall vote.
So to the parent: they have less seats - that % was just over 50% before. It's significant because they've been 20%+ ahead in the polls before the election was called - and we've heard predictions of them getting a 50-100 seat majority. They certainly weren't expecting to lose seats.