I would hazard a guess that the reason they are 'short' on pilots is because they can't find enough people with the required enthusiastic, green type, charismatic personality to pass the BS selection processes.
It's seems it doesn't matter how well your sim goes if you can't demonstrate a time you delivered excellent customer service, in fact you might not even be offered a sim if you can't answer that question
. IMHO, recruitment and selection format is one thing Ryanair got right!