The reason the Tanfoglio clones are popular has more to do with innovation and meeting customer demands better than CZ.
Tanfoglio started out making virtually exact copies of the CZ-75 when CZ was still not importable from what was still a communist country.
The situation changed after CZ became importable and Tanfoglio started improving the design.
CZ has traditionally been very slow, even reluctant to upgrade or offer options, while Tanfoglio has been driving the design.
Today, it's Tanfoglio that's the innovator, and CZ that's the follower and copier.
This started before the CZ was importable, when CZ announced they were going to offer a new Commander-type rounded hammer. This new hammer was going to become available in 5 to 8 YEARS.
Tanfoglio introduced their new Commander hammer THAT year.
Tanfoglio was the first to offer:
Calibers other than the 9mm.
A larger frame for the 10mm and .45 ACP.
Conversion kits.
Better sights.
Ambidextrous safeties.
Wood grips as standard.
Full-length guide rods.
The now industry standard spring-loaded plunger that lifts the trigger bar.
Finishes like stainless steel and hard chrome.
"Race gun" versions.
Longer slide versions.
Polymer versions.
Compact versions.
A firing pin lock.
Frame grip grooves.
And many others.
One area where Tanfoglio has been more innovative is in their triggers.
CZ has been very reluctant to change the original design which puts the trigger very far forward in the trigger guard, and which has a rather poor trigger shape.
This makes the reach very far for most shooters.
Tanfoglio changed the trigger to one that lays farther back in the guard, reducing the reach, then quickly altered the shape to give the trigger an even better curve which made the reach even better.
CZ has only recently begun to offer the Tanfoglio type trigger on some models, but still uses the old design even on large guns like the CZ-97B, which is virtually unusable for people with smaller hands because of the trigger.
Another example of CZ's unwillingness or inability to meet customer demands is that many CZ guns do not have an ambidextrous safety, and no ambi safety is offered as an option or after-market accessory.
If you want an ambi safety on a CZ, you have to have a gunsmith fit....a Tanfoglio accessory ambidextrous safety.
So, while Tanfoglio started out as a straight "Clone" maker, they quickly began to adapt to the market and offer options and upgrades, while CZ remains a much more conservative company that now follows Tanfoglio's lead.
Due to their innovation and cheaper price, Tanfoglio has established themselves in the market by offering what CZ is unable or unwilling to offer, and at a better price.