I think you have the directionality backwards. Trump is not currently in office or in control of the government, therefore he doesn't have the ability to constrain Bezos' first amendment free speech rights.

If Bezos chose to constrain his own speech due to some perceived threat to his companies from a possible Trump administration, that's still a private decision (and an exercise of his first amendment right to non-expresssion).

To be a first amendment violation, the government has to constrain speech (via force or threat).