How does one learn to think about companies buying each other. It’s counterintuitive to me for an entity with stock to buy stock in another entity which could itself own stock in the first.

The way you write it I can’t see why WB would be allowed to sell itself when it makes the most sense for Patamount to go bankrupt some time from now and be split up amongst US media; Netflix/HBO/Disney/Peacock

You're missing the key part. The Paramount deal includes billions in Saudi money funneled through the President's son in law.

What matters is if paramount can pony up enough money to buy. Stores don't reject your cash even if you are debt.