Our personal computers cannot be relied upon to withstand fires, floods, and lack of interest from family members in finding and preserving our work--as much as we may dearly hope that would be the case.
The only real solution will be to get the attention of policy and innovation team members here at WikiTree to think of solutions going forward. WikiTree will be able to provide some means by which we WikiTree genealogists can create profile placeholders for known family members, which are not deleted wholesale, but rather are placed in some kind of waiting area where WikiTreers who created them can hopefully at some point get their parents or even the children themselves to adopt their profiles. This would thus be involve future policy decisions (might want to add the keyword "POLICY" to this question), as well as possible future improvements (you might want to add the keyword "IMPROVEMENTS" to this question to get those peoples' attention).
I am writing this answer because I feel your pain, and I have made similar decisions to yours with regard to moving my genealogical research off my computer and over to WikiTree, and also with seeing profiles I've recently established for family members vanish overnight.
As horrible as it's felt to undergo aspects of the GDPR this week, now that so many profiles missing death dates for people in the 1900s have 'gone dark' and so many children's profiles have gone missing--I expect the innovative in our midst are even now brainstorming ways to better collect and preserve our shared family tree history.
For while we all know that of course we can attempt to preserve family data and history on our own personal computers, most of us have had enough computer crashes, fires, floods, and other situations to realize that counting entirely on passing information along that way can often be an exercise in futility.
PS -- It is worth mentioning that I've been working with computers since the 1970s (including programming them, and working with backups and disaster recovery and information security). In that relatively short span of time, I've seen computer hardware and software become unreadable and unusable by myself and others, due to new systems working completely differently. Part of the appeal of WikiTree's stated mission is that it will strive to maintain the ever-improving vast body of information we are collecting, and keep it secure and backed-up. There really is no private individual's system capable of making similar claims, in my opinion.