Question: Why are bundle customers directed to the cart page instead of the cart drawer?
Answer: Bundle Builder was designed to primarily integrate with the cart page. The app uses Shopify's draft order system to generate orders, then adds these draft orders to the cart page.
Bundle Builder can integrate with your theme's drawer or Ajax Cart. However, when a customer creates a bundle and proceeds to order it, they should always be redirected to your cart page by default - even if the theme is set to use the cart drawer.
If you're not confident with changing code yourself, we'd recommend finding a Shopify Expert to work with. HeyCarson and StoreTasker are recommended partners of Bundle Builder - both specializing in website development and offering free quotes for their services.