What is the evidentiary burden on a plaintiff to explain to the court why it was dismissed?

Paragraphs 49-50 of the decision read as follows: 49. I therefore conclude that in moving to set aside a registrar’s order dismissing an action as abandoned under rule 77.08 there is an evidentiary burden on the plaintiff to provide an explanation for the delay. This includes the delay between the time the statement of claim was issued and the time the action was dismissed by the registrar as well as the time between the dismissal and the motion to set aside the dismissal. This must include an explanation as to why the plaintiff was in default (resulting in the dismissal) and whether the plaintiff moved promptly to set aside the dismissal. If there is no explanation at all the court cannot determine if the delay was “intentional and contumelious” or alternatively as a result of inadvertence or negligence and, if the delay is inordinate, whether the delay is “inexcusable” or if there is a reasonable explanation therefor. 50. If the plaintiff explains the delay and the reasons for the default, then the test set out in Hudson v. Colliers Macaulay Nicolls Inc. applies and the dismissal by the registrar should be set aside unless: a) The delay or the default has been intentional and contumelious; OR b) There has been an inordinate and inexcusable delay giving rise to a substantial risk that a fair trial would not be possible; OR c) There would be actual serious prejudice to the defendant if the action were not dismissed.