As always, when postulating anything about what "they" are doing, or plotting, or intending … 

… ask "who is «they»."

Who is behind Tether?  Would they have been in cahoots with your conspiratorial "they?"  Have they (creators and operators of Tether) been subverted?  Co-opted?  Enlisted?

Conspiracy theories mostly don't work when you analyze the mechanics and the specifics.

How would Tether be of any benefit to the factions within, and behind, governments who are (or may be) seeking to implement central bank digital currencies (CBDCs)?  How would that work in their favor?