The economics of AM doesn’t make sense for any other station bar ethnic stations who have listeners who have AM radios and Caroline who have a big audience who are enthusiastic about old fashioned transmissions.
However, the future is internet and smart speakers at home, 4/5G for long distant travelling and public transport and DAB for cars who have shortish travel journeys which is the majority of car travel.
Therefore Caroline should pitch their transmission methods accordingly which from where I sit they are doing within their limited budget.