Vetoing it would have disassociated Trump from it and energized his base. Now Trump is firmly attached to it and he’s delivered a gut punch to his base. There was no reason for him to sign it. There was even less reason for him to tweet about not signing it and then sign it the same day.
The vote totals indicated the veto would of been overridden.
I agree he should of vetoed it and made all the slime come back to DC to override.
Sometimes in life, fighting, and losing, is better than not fighting at all.