Legum explains that Trump has promised he'll hand over his businesses to his children when he becomes president (but has been vague about the details). Then he invites said children; namely Donald Jr., Ivanka and Eric, to the meeing with the tech giants.
In other words, it appears to even the untrained eye that Trump is using his postion of power to further his own business interests, which isn't very presidential.
Many other Twitter users agreed that it was an 'assault' on democracy:
@JuddLegum They don't even have the courtesy to try to hide it. It's like they're just daring someone to do something.