Then there it was, an ad for “Joe’s Café,” perched atop a metal pole, which was upright under a cape of kudzu vines. Maybe it was the way the setting sun illuminated the yellowing plastic. Maybe it was the small hole, evidence of vandalism or of a hailstorm. Something about the sign touched me. I pulled over.
Is the bold text a appositive clause or relative clause?
If it is a appositive clause, then why "that" is omitted? Is it acceptable? I am only aware of the rule that "that" can be left out in relative clause and objective clause.
And if it is relative clause, should it better be "Maybe it was the way by which the setting sun illuminated the yellowing plastic"?