Despite it being the album which essentially led them to continue? Together with the departure of Ant Phillips, Abacab was possibly the most important aspect of their career in terms of the threat to their longevity.
I don't disagree but as somebody who had been a fan for several years, the change of direction was quite a shock. I always attribute this to the increased influence of Phil, whose writing seemed to be going in a different direction more towards the shorter popier songs. The band clearly enjoyed the extra sales and exposure this change of direction gave them. I agree it's quite possible without this they would have split. I heard Abacab but didn't like it and so Duke was the last studio album I bought. I have continued to enjoy them live and continue to buy their live output.