Database
db={coll:[{a:2,surveyTargetHobbies:["65f63f7c4006ec749ffae6f8","65f63f7c4006ec749ffae6f9"]}],hobbies:[{"_id":ObjectId("65f63f7c4006ec749ffae6f8"),title:"a"},{"_id":ObjectId("65f63f7c4006ec749ffae6f9"),title:"b"}]}
Query
db.coll.aggregate([{$lookup:{from:"hobbies",let:{vid:{$map:{input:"$surveyTargetHobbies",in:{$toObjectId:"$$this"}}}},pipeline:[{$match:{$expr:{$in:["$_id","$$vid"]}}},{$project:{_id:0,title:1}}],as:"surveyTargetHobbies"}}])