There is a bug in the 20w45a snapshot some of the mobs are not moving and fire water and weapons are not hurting them there like ghost and the nether trees are not there.
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Can Confirm in snapshot 20w45a. Reloading the game fixed it, but it happened with skeletons and creepers for me
Mob ghosts and missing nether trees are two different things. Please put both issues in separate bug reports unless you can link both these bugs to one error.
Regardless both are duplicates MC-203574
Can you provide a video of the glitch with F3 enabled?