Firstly, don’t feel guilty at all about anything! I have been through the ringer matching up my various buns over the years and also dealing with chronically ill buns (including one that I was fostering to try to bond). I know it can be so heart breaking to return a bun after a failed attempt.
I wouldn’t have advised to try to bond with a megacolon bun anyway, because they require such special care it would be really hard to have them in a bonded pair (dietary differences, poop monitoring, etc, as you know). Plus it’s important for both rabbits to be healthy to bond, so it would have not been a great recipe for success.
Second, you tried many rabbits and none were a great match, so it’s not like you didn’t try! That doesn’t mean he’s unbondable, but it means you don’t need to force anything. If you would like to try again in the future, just keep in contact with the rescue and they can let you know when there might be some good matches there. There have been buns on this forum that seemed very clearly “single buns” that wanted nothing to do with another rabbit after going on many dates, and then suddenly they found a match. Who knows what’s going on in those little bunny brains?
I don’t want to get on a soap box about the push from certain prominent social media channels about free-roaming, but personally I think it can be harmful when stated as a “must do”. Many rabbits (and homes) are not suited to this, and it can lead to rabbits being rehomed because the owner was not prepared to have alternate housing. I think of it like dogs… many people crate their dogs when they are not home, and this is widely accepted. As long as a bun has appropriate housing and gets exercise in a larger area, they can be completely happy and healthy. I’ve even noticed my buns are MORE active when I’m not giving them full free-roam (I had one pair that was perfectly behaved so I started letting them roam 24/7, and all they did was lay around!). So don’t feel bad about that either!
There is absolutely no need to rush or feel pressured to bond. It’s important that you feel rested and ready for the process, and excited about the bunny you will adopt. Bunnies also need sleep and rest, so don’t worry about not interacting with him all the time.
For the future, I tend to not rely too much on seeing amazing positive interactions in inital speed dates. I like to use speed dating as a way to make sure the rabbits don’t HATE each other, because they will often behave very differently in the shelter environment. I suggest (if and when you try again in the future) that you go meet some rabbits and pick out 3 that YOU really like, then try dating those. If they don’t attack each other, then they are likely bondable. Male-male pairs are also pretty common, so you might try another male as well.
.
.
.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.