Shouldn't Startups like "new"? Lessons learned

I have now had 2 different roles where I was responsible for building a new capability in a startup technology company.  Both ended much quicker than I had hoped, so there should be some lessons learned, right?

My first role was to create a professional services capability in a video streaming company.  Customer facing, expected to bring additional revenue, not a core competency of the company. My second, building Customer Success for a very early stage data analytics company.  Again customer facing. My responsibility was to put customer success process in place and deliver more satisfied customers, and again not a core competency of the company.  Both require non-technical skills for the most part - at least that was my belief.

What are the lessons I learned?
1. It is hard to create a new capability in a startup. There is typically a very narrow focus in an startup  (by necessity) and so adding new capabilities adds overhead and is distracting.  Ownership of the initiative from the top is essential because of this.
2. A new, customer-facing capability is as much about what the customer needs as it is about what the company resources can (and can't) do.  A balance is required so you don't promise more to the customer than your company is capable of delivering.
3. You need to be technical.  Even if you don't think you need it, you need it.  I believe this is primarily true in a startup vs. a more established company that has adequate technical resources.   Sales is the only organization in a startup that can claim they aren't technical and get away with it.
4. Over communicate what you are thinking and doing.   And really think about how that communication should happen - many senior execs want to talk, not read email. And no matter how you decide to communication generally, have the difficult conversations in person.
5. Don't expect your senior management knows what you are doing.  In a startup it seems there is generally less communication between people because everyone is overburdened with things to do and there is less process to keep people close.  If you are not directly reporting to the CEO, they probably don't have a clue about what you are doing unless you have consistent contact with them.  Make that a priority.