Yes Leica is comparatively very small but Canon is in a lot of businesses beyond photography and optics which contribute to that turnover... Eg they are a major player for printers and for expensive medical diagnostic systems/scanners etc. Leica has a much smaller footprint in that market.
I'd be more interested in profit figures rather than turnover - and wonder if the % margin may be quite different between the two companies?
Yes, maybe Nikon would've been a fairer choice. Their imaging division's 2021-ish revenue was ~US1.1 billion (if I've got my yen-to-dollar conversion right).
Dunno about profit margins. I'd guess Leica's margin is higher as their strategy sure looks like "serve niche market with requisite volume (low) and price (high)."
-Dave-