(Maybe 'cause of the neon signs triggered by testimonies and audits, etc. emitting from these towns)
I mean really. Your Q is like saying why are rapists arrested in one state and murderers aren't in another. Or why are robbers arrested in one state but child molesters aren't in another. For the most part, crime is crime and is treated by such by law enforcement officials. If anything, polygamists got the benefit of sympathizers in 1953 when the feds raided these cities...and law enforcement stayed away from them for years despite this community-wide law-breaking.