Speaking without thinking is something I can understand, but it's not an excuse. Nobody is an island, we're all standing on the shoulders of giants, and disparaging another's work when they're arguably helping improve your own project is an attitude I wouldn't expect in an OSS project. As someone else said, if this is the way the author felt about Tailwind, they could have chosen a proprietary license, or just left it without a license to fall back on regular copyright.
What happens a lot of the time is that authors choose open source licenses because they know that's how their project will attract attention. I'm not saying that's necessarily what happened in this case, but it's not uncommon to see authors of some OSS projects seemingly being surprised about how OSS works or what the mentality is expected to be in the project.
All true! But to invoke a common ground here, most people put up a lenient license in the beginning thinking I will attract some attention and if things pick up I will create a product(or some serious library) out of it, make money, while leaving the core as is. But when it surprises them they are not ready for it(which is pretty much all of us). In fact, if I were to guess the OP would have just dropped the original project if it were not for the pacing provided by the Tailwind CSS team. The thing is for most of us personal projects are a way to express our autonomy where you do what you like and want instead of being constrained by some guy telling what you can do, which tools you can use, what features should go in etc, which is the case with most jobs; this autonomy allows you to walk away from your project any time and when that autonomy is played with by anyone who you did not originally see as an ally it can be upsetting. Tbh, it would be naive to think that OSS is still an altruistic movement, maybe some still go by that, but the commoditisation with GitHub becoming your Resume has only made it a more selfish endeavour.
Actually I agree with you and it doesn’t make sense to rant and pity oneself on the Internet, but I think this is a natural consequence of what is being made of OSS in general.
What happens a lot of the time is that authors choose open source licenses because they know that's how their project will attract attention. I'm not saying that's necessarily what happened in this case, but it's not uncommon to see authors of some OSS projects seemingly being surprised about how OSS works or what the mentality is expected to be in the project.