Dropping marketshare for others may not mean falling business. It's possible that the market size is growing fast enough for the commercial ones to actually be seeing a growth in business.
This could definitely be true. I've set up SSL on a bunch of sites that otherwise wouldn't need it at all just because the Let's Encrypt client is so easy to get working.
Every CA is growing except StartCom who were distrusted by most players last year (and Microsoft, belatedly, remembered this year) and have recently declared they're throwing in the towel, won't try to get back their trust.
The big categories which shrank are "None" and "Invalid Domain", ie people who didn't have SSL, or were on shared hosting and never switched it on for their site or whatever.
Is your hypothesis that Cloudflare doesn't _pay_ them for those certificates?
How about cPanel and others who bundle Comodo certificates?
No, I think Comodo are doing very nicely off this. They've correctly judged that they're never going to be the Maserati in this industry they need to be Ford or Toyota and too bad if some people sneer.
This is especially likely given that many sites considered HTTPS in earnest only when Google started aggressively factoring it into search rankings or when they needed HTTP/2 for performance. Search & site speed are a lot easier to make a business case for than privacy, unfortunate as that may be.
