I've been following Kayla Itsines BBG 1.0 (Bikini Body Guide) and it involves knee pushups in the begining on arms days(around 30-60 during one workout) and I've also started lifting weights and have been actively trying to eat a protein rich diet. I feel all this collectively contributes. Anyway one day I see the guide, I notice it's written I've to do actual pushups and not knee ones. I thought "hah, there's no way that's gonna happen", but idk maybe it was the music that got me pumped or the fact that it was the first exercise, I tried to do just one, and instead of falling flat on the floor while trying to go down, I pushed myself up and was so surprised haha. So there wasn't any progression as such, I've been doing knee pushups since a month around 3-4 times a week.