Actually, the algorithms have a lot of overlap. The original CRDT (called WOOT, for "WithOut Operational Transform") was derived from an OT algorithm.

Historically, what happened was that the OT research community couldn't solve consistency without adding tombstones into their data structures that recorded deletions (and generally kept these deletion marks around forever). They called these "tombstones." People didn't like that you had to keep them around forever, but they seemed to solve the problem.

Over time, some researchers decided to just keep more things around forever, and promoted the idea that you don't need to do as much transforming of operations if you just preserved all operations in a spatial data structure, not just the tombstones, but everything. They came up with a new name this style: CRDT.

But in fact, the technical definition of a CRDT actually fits OT algorithms quite well. A CRDT just means that you can accept any operation at any time. That's what a good OT system also needs to do. So there isn't a technical distinction between an OT or a CRDT. They each define a set of features, and your synchronizer can possess OT features, and it can possess CRDT features.