Although I've personally not been impressed with Dewalt cordless tools, I wouldn't consider Dewalt a DIY brand either. My experience was also 10+ years ago and comparing them to Makita. They were not junk, but for the price I felt they should be better.
Dewalt's corded tools have been generally been solid. Their orbital sander and trim router are highly recommended by many woodworkers.
That brings up another aspect though, it is not just regional, but which trades. Dewalt and Makita tool offerings skew towards carpenters. Milwaukee offers quite a few tools desirable to plumbers, electricians, and mechanics which will draw them to that brand.
TTI also owns Milwaukee in addition to Ryobi, as well as producing the regular Ridgid brand power tools. (Not the actual professional plumbing tools, although some may use TTI components).
Chervon is an OEM manufacturer making tools for other brands in addition to FLEX, Skil, EGO, and Skilsaw (the higher end version of Skil).
Bosch in addition to worldwide distribution also manufactures special tools for industrial use, that don’t even appear in the regular Bosch tool catalogs or websites.
The “industrial use” tools may be supplied to industry for assembly purposes, and have significantly higher prices than the average power tool.
The Bosch AMPshare battery platform may also help the numbers.
TTI also makes Hart. While Hart is almost invisible on this forum, being the "premium" brand of the largest retailer (Walmart) in the US can't hurt TTI's over all sales figures.
Bosch also owns a several popular brands of consumer goods (dishwashers, coffee makers, vacuums etc) as well as Dremel which further muddies their actual share of the tool market.