It is a manner of speech. Consider:
'but they have not gathered much support until recently'.
In your sentence the speaker has put the emphasis on 'only recently'.
Had they left sooner they would have caught the train.
If they had left sooner.......
There was a delay which, had they not decided to come, would have saved them a lot of distress.
Because they decided to come the delay caused them a lot of distress.
This is all part of the way we speak.
Student or Learner