I can explain a little bit
1- KYC, the bank is a highly regulated entity, regulated by the state, they are a branch of the executive, they enforce banking laws set by the legislative, and can get involved in cases of fraud, money laundering, or other illegal activities.
If they see a million dollar transaction, they usually want to know where the money came from, if they don't they would essentially be looking the other way.
In general know what your business partner needs, in any walk of business. Let them know that you have a such and such business, that you got a round of funding. Also know what kind of bad actors you want to differentiate yourself from, let them know you are not a drug dealer, you are not laundering money, or running a ponzi scheme, and that the money won't be frozen putting them in trouble.
2) Money is a very complex subject, the fact that you think of money as "something that is stored in a bank" is testament to the fact that banks do a good job, it's an illusion, there's a lot going on behind the scenes that you are unaware of, similar to how there's a lot going on behind the scenes in Google or ChatGPT, which have simple interfaces but complex inner workings.
3) In general, a bank is a vendor, a supplier a business partner, you pay them for services. Maybe in your personal life you don't care and you are used to anonymous transactions because of the low amounts. But in business, these are strategic relationships, you want to get the most out of your money and establish a relationship with your vendor. Loyalty goes a long way, although switching vendors is always possible, it's a tradeoff with consequences that needs to be considered, and not ignored.