The Astro2020 decadal survey recommended a ~6m IR/O/UV telescope equipped with a coronagraph instrument to directly image exoEarths in the habitable zone of their host star. A telescope of such size may need to be segmented to be folded and then carried in current launch vehicles. However, a segmented primary mirror introduces the potential for mid spatial frequency optical wavefront instabilities during the science operations that would degrade the coronagraph performance. A coronagraph instrument with a wavefront sensing and control (WS&C) system can stabilize the wavefront with a picometer precision at high temporal frequencies (<1Hz). In this work, we study a realistic set of aberrations based on a finite element model of a slightly bigger (8m circumscribed, 6.7m inscribed diameter) segmented telescope with its payload. We model an adaptive optics (AO) system numerically to compute the post-AO residuals. The residuals then feed an end-to-end model of a vector vortex coronagraph instrument. The long exposure contrast thus obtained is finally used in an ExoEarth yield method calculation to understand the overall benefits of the adaptive optics system in the flagship mission success.