Mining reward is not the security budget - What does this mean?
Miners are responsible for picking transactions from mempool, nodes just verify that.
"People" ate interested in run miners is not true. Big corporations do, people have been eliminated by ASICs only mining protocol.
Mining is profitable, is true. But that's the current state. Mining's profitability is decreasing with every halving. That's why mining went from people doing it in their basement to 2 companies doing nearly 60% of mining.
Again to the point that miners are not security budget, definitely it is. If US Govt spends few 100 billion (which is nothing for them) and setup mining rigs, they will quickly gain majority hash power and when they only allow KYCed transactions, mempool will keep getting filled up and my transactions will take not hours, rather days.
Mempool filling up also increases price, thus pricing out more users out of the network.
About the first line of your post - I am in bitcoin since 2014. And building distributed infrastructures for tech companies is one of my income sources.
And halving and bitcoin's usd price has any correlation threory goes out of the window when you open a Nasdaq 100 3X leveraged ETF chart vs bitcoin USD price.