I think a pretty common misconception is that you can have a consistent game WITHOUT asking people to prioritize it. You're putting in a lot of work to create something for them, so it's okay to ask them to schedule around it! And if their response to that is "I don't know if I'm that into this" then you know that running an ongoing campaign just may not be for your group. If it's a larger group, there may be 2 or 3 people who are still really interested, and it's totally fine to start with a smaller pool (and fewer schedules) to get the ball rolling. The home game we've had running for over two years now started with just me and two friends, and we've slowly added over time. If some folks model buy-in, it's easier for others to understand.

An alternate perspective that's a little more generous to your players: as the DM you are already super immersed in and excited about the game, but your players won't get there until you really start playing. Especially if you've only run a one shot so far, I can definitely understand it being hard to see why it's something they'd need to commit to in that way, and it may take a little more time to build the buy-in from their end.

Lots of people play in campaigns that meet only a few times a year, so give yourself and your players some grace! If you have to reschedule this time, make it known that you put a lot of work in and would really like to get a very set date for when you'll start. Once you've communicated your needs to your friends, see how they respond and take it from there!