I ask because contracts typically, despite their duration, contain a variety of exit clauses. In this case, Amazon could argue they were exercising a "compliance with laws" clause (if it was in the agreement) such as,
"<Licensee> will not use, or allow its products to be used, in violation of any laws or regulations."
It becomes a legal argument as to whether Parler's members that advocated violence against the government caused Parler to violate the clause, and whether that amounts to a material breach that triggers contract termination.
That is very different than a blanket statement that Amazon "breached that contract and bowed to the mob." In fact, Amazon can sue Parler for breaching the agreement and exposing Amazon to significant liability for (at the most extreme) aiding and abetting terrorism.
Note that I'm not arguing either way, simply stating what lawyers are likely discussing behind the scenes.