The problem with "deletionism" is not lack of sources and citations. It's the fact some moderators don't want certain material there. Creating sources is not a guarantee you'll be able to add them back, quite the opposite.
In the past I've seen purges of all kinds of well-sourced material: law, electric engineering, literature, important CS/engineering figures. It's never because of lack of sources, it's always some subjective rule.
Actually, I've seen "the content is already available in another website, why do we need it here?" being be used as an argument against reinstating some very uncontroversial articles.