I too have severe Crohn's Disease and had an ileostomy at the end of June. Crohn's affects anywhere from the mouth to the anus, so you can't make a blanket statement that once your colon is gone, you'll be cured. There is always the chance that other areas could be affected. That being said, I absolutely suffered with my Crohn's. I had two bowel resections to remove areas of the colon with severe scarring and strictures but still suffered from the symptoms of many bowel movements at all hours of the day and night. I tried 6MP, Humira, Stelara, Inflectra, and most recently, Rinvoq with limited success and never really got to remission. My Crohn's affected every inch of my large intestine and the anastomosis, and I had a few years where I would get anal fistulas that were very painful and required the placement of setons by my colorectal surgeon. I was told by the team of colorectal surgeons that individuals such as myself who have multifocal strictures in the large bowel, anastomosis inflammation, and anal fistulas (the trifecta as they referred to it) see a great outcome after an ileostomy as their data showed. I still suffer from joint inflammation, but now have that under control thanks to my rheumatologist and taking sulfasalazine.
I can say that after the ileostomy, I no longer have the harsh gut pains I had with my large intestine. That pain and discomfort is just... gone. I don't have any urges to run to the bathroom for a bowel movement, which is a nice change of pace. I haven't had a great experience with having a bag so far, but I'm optimistic I'll get it figured out. I didn't have a choice in my surgery. It was have an ileostomy or die, so it was an easy decision when you really only have one option.
After my surgery, I've been in touch with a gastroenterologist at the Mayo Clinic for the next steps as far as medication goes. He said that three months after my surgery, I should have labs done with CRP and fecal calprotectin to measure inflammation levels in the small bowel. Repeat this at 6 months if there is little/no inflammation and have an ileoscopy (colonoscopy through the new stoma). If there is no inflammation, I can stay off of Crohn's medications.
It's a life-changing procedure, but there are a lot of resources out there, and hopefully, you have access to a good hospital/GI doctor that can answer any questions you may have.
I wish you the best of luck. Sorry for the lengthy response, but I hope it helps.
Josh