You can still have a thank-you page that has an offer, but you need to give clearer instructions to your audience.
Say something like - "Thanks for signing up! Your free ebook will arrive in your inbox in just 5 minutes. While you wait, go watch this video here, it teaches you [insert sales pitch]" and then have the page AUTOMATICALLY REDIRECT after 5 seconds or so, with a button to click-through faster.
This way the readers are like "oh thats cool I need to kill time before I go back to my email inbox and get my ebook, hey why don't I go watch this interesting video."
^^^ That is how you do it.