I've heard a lot of conspiracy theories but nothing solid.
The dismantling of the Knights Templar is really dramatically overstated.
Sure, some were arrested, tried, found guilty and killed (particularly in and around France) but most of them just got rolled up into the Knights Hospitaller Order.
In fact, Knights Templar continued to exist under the name "Order of Christ" in Portugal for another 400+ years.
The idea they were wiped out in one fell swoop of great betrayal and treachery is wholly false.