The EZY timetable was changed in April this year to provide more popular departure times, which according to my observations has led to a significant increase in passenger figures for their Liverpool service.
This may not be easily compared to the April 2010 numbers, although the 13,000 figure is a marked increase over the c.9400 in April 2009. But it may represent a shift towards the Liverpool flight from the Manchester Flybe route. I've used the flight several times since early April as it's a big saving over the Flybe prices (even taking into account the extra travelling to Manchester). Many IOM customers are not actually travelling to Manchester or Liverpool, so both routes can be equally inconvenient.