Indeed, walking punches way over expectations for keeping weight off. You have to do a good hour of a walk, but an hour walking is probably better than a rushed workout of similar time.
Good on you! Something I preach to my children is that success comes from showing up every day to do a little and not from a sudden burst of a lot. Well done.
I turn 50 this year and have committed to doing 50,000 pushups before 2024. It sounds like a lot, but after the first month, doing 200-300 a day isn't really that difficult (when broken up into smaller sets). Honestly, it's a LOT more of a mental challenge than a physical challenge.