Ashwin scored a century in a pitch when the top order players are struggling and there is plenty of time left in this match and two days is more than enough to pick the England wickets, India is leading with 471 runs and they will try to frustrate the England players and they will be tired when they come back to bat and that is the plan as they keep on batting the entire day.
Ashwin is from the same city and he was probably accustomed to the ground conditions. The England bowlers (especially the spinners) lost it after the first 1-2 hours of play, when Kohli and Ashwin built the partnership. Ideally the England captain could have used the pacers (Olly Stone and Stuart Broad), but for some unknown reason he was reluctant to do so. In the end it was Olly Stone who got Ashwin out.