His scheme proved easier to execute than he expected.

Vane unconsciously played into his hands.
After his bitter disappointment through not meeting Lavinia at Rosamond's Pond, Vane walked back to his Grub Street lodgings plunged in fits of melancholy, alternated with moralisings on the faithlessness of women.

He did not believe Lavinia had kept the appointment.

As for Sally Salisbury, well, it was unfortunate that he should run across her at a wrong moment, but he never imagined that the meeting with her was one of design and not of accident.
Vane had the poetic temperament.

He was human and emotional and--he was weak.