Well, they ask questions both online and offline. And considering the fact it wasn't monetized from the onset, I just can't find it being monetized anymore. Tho I'm doing this for bitcoin too, the stress isn't easy.

Yep, I hear where you’re coming from , definitely an awkward situation. I suppose you’ll just have to put it down to experience and bite the bullet this time !
A good way to get out of it is too explain that the most important part of bitcoin is DYOR! Tell them to do it themselves and then give them a specific time and/or place that any queries can be explained to them.
For future tutorials talks if you doing it for free, explain that you are giving up your time etc and then you can monetise all future correspondence.
As long as it’s explained at the beginning, you shouldn’t encounter this problem again.
Hope this helps and good luck

There's really nothing wrong with it in my opinion. Organizing a seminar/meeting is going to need a crap ton of time and effort regardless of size that I'd be damned if I don't earn a reasonable amount of money for managing one regardless how passionate I am with Bitcoin. Just price things reasonably, and completely make sure that you're actually putting out good content, and it should be completely fine. Make sure that the attendants leave the seminar/meeting with knowledge that's worth a lot more than they paid for.

I think that it's fine to monetize any meeting, Bitcoin included. If you are wealthy, and you're doing it like volunteering, surely you would not collect money. But if you are a person who wants to do something good but also kind of needs money, it's fine. In that case, you have various options:
1. Set a fixed entrance fee.
2. Set a 'pay what you wish' fee.
3. Find a sponsor of the event, so that you get paid but participants don't need to pay.

In my opinion no because knowledge is expensive and this is clearly seen in our education structure of the world. I believe you guys spent ample time and resources getting to know more about this industry so if you are to offer people such knowledge on a regular basis then i think you have every right to monetize it. There are cases where you get to teach someone a quick thing about crypto and i would not encourage you to monetize that but if it becomes regular like going to school then you need to be paid.

Do whatever you want. If you feel you should be compensated then put that out there.
I don't know what sort of meetup you hosted or what the idea behind it was. If you are bringing complete newbies into the space though, you should expect follow up questions. Were you planning to host these meetups on a continual basis? If yes, you should tell them to send their questions and you will address them at the next meetup. This helps create boundaries and sets expectations for when they should expect answers. The meetups themselves could then be centered around answering group questions - these could be pooled or asked in a discord channel or something similar and anyone could then brainstorm/research the answers.

Now some people just want to be spoon fed everything so for them you could promote yourself as a paid tutor/guide. Set a fee and if they are willing to pay it then there you go, if not, then you can explain it's a service you provide for a fee. I've attended a local meetup that's been running for years, and they also do another one strictly for newbies. The one I attend has a 5$ fee, that covers a delicious meal and coffee though so it's not exactly the same thing. They are just trying to grow the crypto space.

It really comes down to what your plan for these meetups was, and how you want to execute it.

I would if I were you. You are allotting your time, resources, knowledge and expertise to train them, and that's alone IMO is already a justified reason on asking a small fee. Kind of like a small crash course that some institutions are offering nowadays on different parts of the world. Knowledge is indelible and valuable, and it's not something that one can stumble upon and grasp so easily without having someone to learn from or some resources to use.

I'm pretty sure they'll think of it as something not worth their time but just own it. Show them and make them feel that you know what you're talking about and you're worthy of being compensated into helping them learn new things.

Why do you think this is wrong? You spend your time, resources, you share knowledge. In my opinion, you are a real tutorial, so this should be rewarded. You just need to do monetization right to make everyone comfortable

If you want to monetize your efforts that is fine but you need to put some boundaries, there are people like that in all industries and the people that give seminars soon realize the problem you are facing, so you need to learn how to not waste your time after the seminar or they are going to consume all your time, this is especially true for those that did not assist, tell them you will send them a notice when there is a new seminar and then cut them off, you cannot explain this kind of thing one by one or it is going to take you forever.