As Jonathan Chait notes, Trump's racist attacks, threats of revenge, and howls that his election losses, past and future, are illegitimate have elicited this response from the GOP establishment: his campaign is undisciplined, which is pointlessly alienating swing voters.
But Trump's strategy, in embracing insurrectionists with promises of pardons and pledging to jail opponents (while sweeping aside allies displaying insufficient zeal), is to crush out any traces of dissent within the party. His aim is clear. He is signaling to all who will heed, especially those who will serve in a second Trump administration. He won't be bound by Constitutional or legal constraints. And neither will those who do his bidding.
An effective Trumpist government has difficulty functioning under the rule of law. If Trump’s staffers and allies believe that carrying out his orders, some of them plainly illegal, will lead to prison or other punishment, they will again hesitate to follow them. That belief is one he has to stamp out, especially as he faces multiple criminal charges for his attempts to steal the election in 2020.