No one cares about why your ad ended up not performing.
No one cares that the client changed it all.
No one cares that some guru told you to do it.
No one cares that you were unlucky.
The customer doesn't certainly care about all the marketing logistics that happen behind the scenes.
Because at the end of the day - the only thing that is left is your brand and the customer.
The relationship between those two things and ultimately - the customer - decides if that brand or piece of marketing you created is worth keeping around.
Not your excuses.