It may be that Trump cannot destroy the GOP, that Lowry has misplaced where his worry should go. The question seems to be, is the GOP, in Lenin's words "ripe and rotten-ripe" for collapse. That is as he says, "It would be absurd to regard the whole question as one of personalities."
Of course plenty of commentary has focused on the roots and development of the current state of affairs - Goldwater, Atwater are among the frequently mentioned authors of these fluid dynamics, the "reap what you sow style" of punditry.
So Trump may only be the messenger, able to neither destroy or, through huge acts magnanimousness, save the Party.