In a larger company or outside it, a startup’s survival depends upon a relevant, effective strategy and brilliant execution.
Execution in all functions is important.
For instance, a semiconductor design company will need to have excellent operational execution capabilities to design, test, manufacture (or have manufactured these days) and then take their technology to market. Win those design-ins and proliferate their chips into the right markets, customers so that you have delighted end users.
Execution in R&D, Operations, Marketing, Sales are all crucial to success.
A great strategy is a like a story without an ending. A wonderful product wont really sell itself but needs an innovative marketing team and a fired up, get things done sort of sales force.