Some more thoughts:
If someone were to look into the program deeper, maybe it is possible to run an RCT. You could randomly assign some participants who sign up to the program to the control group. You could just send a document to these people explaining how to be vegetarian or something, and not make them join any groups. And then you could send them the same questionnaire to them as to others. This has some flaws but would be better than nothing. But it’s pretty clear that the program should continue so I don’t think it’s worth the effort.
Another mildly useful thing to do would be to check if meat consumption in Israel has gone down in general, and use that as a control group. It could be mildly useful because it would make you dismiss hypotheses that they consumed less meat because of unrelated reasons that apply to all Israelis like increased meat prices, or increased availability of plant-based options, or meat-related health scare.
Some more thoughts: If someone were to look into the program deeper, maybe it is possible to run an RCT. You could randomly assign some participants who sign up to the program to the control group. You could just send a document to these people explaining how to be vegetarian or something, and not make them join any groups. And then you could send them the same questionnaire to them as to others. This has some flaws but would be better than nothing. But it’s pretty clear that the program should continue so I don’t think it’s worth the effort.
Another mildly useful thing to do would be to check if meat consumption in Israel has gone down in general, and use that as a control group. It could be mildly useful because it would make you dismiss hypotheses that they consumed less meat because of unrelated reasons that apply to all Israelis like increased meat prices, or increased availability of plant-based options, or meat-related health scare.
Related: https://veganuary.com/what-impact-does-veganuary-have/