Just a few points:
1. Even though I'd already spent 2 years on the startup, the first co-founder I bought on had the same equity as me. He wanted it, and I wanted someone fully committed.
2. I was off fundraising for 2 months, and my mistake was not communicating that really well with them. I wasn't a great leader at that time. However, I did notice something was off but I just thought it was post-yc depression (which is actually a thing, apparently). I asked them outright if everything was ok, and they said sure, that it would all be fine when we got back to Australia and moved on. I trusted them, and they lied to my face.
3. I think they were very naive, not malicious, in how they left. They thought everything would be fine if they just left, but thats not how startups work.
4. One of them refused to talk to me or give me an explanation after he left. I had to practically force him to meet me for some closure. Its like getting a divorce with no explanation.
I made mistakes too so its not all on them, but at the end of the day a co-founder is supposed to be your partner through thick and thin, and they bailed without talking through the issues at all which equates to stabbing me in the back. And they made sure to tell me this after I'd reimbursed them for thousands of dollars in expenses for their YC adventure.
The purpose of this is NOT to discredit them. I'm not a huge fan of them, but they dont deserve to be villified. I'm just trying to be a bit more transparent about what happened so that its helpful to some readers. I'm sure they've learned from the experience and will treat their next cofounders differently if they do start something else.