How did the encrochat bust actually work?

Sorry if this is not the correct sub.

I’ve been reading accounts of organised crime members being busted after encrochat was cracked. But how did they actually tie these individuals to their encrochat handles? Could they locate the people by tracking their phones somehow? Or did LE just manage to put 2 and 2 together from the message content?

accounts bust cracked crime encrochat manage organised crime people phones privacy tracking work