It is great news to hear you D stopped. One couldn't ask for a better result.
It is possible that changing to the new diet reduced consumption of some things that are IBS triggers easily handled by established IBS dietary management approaches.
Have you had a fructose malabsorption breath test?
My D stopped shortly after I removed specific fruits, honey, agave, high fructose corn syrup, etc from my diet. I have IBS-D with fructose malabsorption.
The approach I used is the mix of the clinically tested FODMAP diet used to manage functional GI disorder symptoms such as those from IBS (see links in my signature) and Heather's EFI diet that has been used by thousands of IBS suffers. Fructose is managed using the FODMAP approach.
I am able to control my IBS-D quite well using the EFI and FODMAP diets. I hope you manage to keep yours under control too.
-------------------- STABLE: ♂, IBS-D 50+ years - Science of IBS