You just explained why Sea World wants a hotel…I think everyone understands that. What you’re missing is why a customer would choose a Sea World hotel. I’m sure they’re out there, but are there enough to fill a hotel 365 days a year for years on end?
If they put up a hotel that could have been copied & pasted from I-Drive/US-192, then there's no point... but there is a draw for a hotel that is branded to SeaWorld, offerings aquariums, unique perks... and most importantly the Sesame Street brand. I can assure you there will be huge demand for Sesame Street-themed suites and character breakfasts.
I don't think we should see this hotel as a competitor to Disney/Universal onsite hotels, but SeaWorld is a brand that is recognizable and could at least draw interest.