In my experience, turning a dissertation/thesis into a monograph is less arduous because you just have to cut out vast swathes of thesis-ese from the prose style, and also there are huge chunks of stuff you have to put in the thesis to show you have done the reading and engaged with the arguments of the authorities, which can be reduced relatively painlessly to two sentences and a footnote (although it's sometimes quite a long footnote). Or whole sections that you can publish separately as articles, and refer to...