Add a clear rule in the lease that homes cannot be removed without park approval and a proper notice period. Offer fair buyback or resale help so sellers choose to sell inside the park instead of pulling homes out. You can also charge reasonable move out fees where allowed by local law to reduce quick removals.
Mobile homes are personal property and like cars can be moved at any time with appropriate legal notice provided in the lease. You may be able to keep the damage deposit and sue or cleanup if lot is left a mess but that is about it.