I think if you look at the satellite imagery on this link you will understand why the Red Arrows deemed the site unsuitable. Apart from a large industrial complex almost on one doorstep of Trinity Park and housing on the other, nearby the A14 is an extremely busy and often congested dual carriageway carrying a very high volume of container traffic from and to the port of Felixstowe. Bulls running amok - yet another interesting dimension.
https:
//www.list.co.uk/place/64541-the-suffolk-showground/