[HELP] Why did my smoked Turkey suck?

I have been tasked with providing the turkey for Thanksgiving this year. I recently got a smoker and thought I should smoke the turkey. Before ruining Thanksgiving, I decided to practice first. I smoked a practice turkey on Wednesday and was not thrilled with my turnout.

The flavor was okay, but it was dry. The skin was crispy but slid off of the meat, sort of like fish.

Details:
15 lbs. Turkey was pre-brined.
I let it set out 45ish minutes before seasoning and stuff.
I stuffed with half an onion, carrots, rosemary, thyme, and garlic.
Sprinkled with a rub called "The Usual" from Fire & Smoke Society (Salt, Black Pepper, Rosemary, Garlic, Lemon, and Cayenne)

Smoker was at 240°
Cooked for about 7.5 hours
Basted with unsalted butter about every 2 hours ( I think just 3 times)
Removed Turkey at 160° and let rest for about an hour

What did I do wrong? I would love it if someone can troubleshoot my turkey problems. Thank you in advance.

TL;DR: Turkey was dry, don't know why.

Edit: Thank you to everyone who responded! It seems the overarching answer is higher heat ~350,°. Unfortunately, my smoker only goes up to 250°, but hopefully this post helps someone else too!