Tarot cards were originally playing cards, so ALL divinitory uses are afterthoughts. There are those who will read only with Marseille-type decks precisely to avoid all the occult claptrap that's been piled onto the cards.
However, even before the tarot, people were divining with cards, and associating meanings to them. Aside from the medieval symbology of the traditional trumps and courts, there is no innate meaning in the cards. All the rest, including whatever numerological system you choose to read the pip cards with, was made up and tacked on. Part of the joy of tarot is its ability to carry all these divinitory/narrative/occult/philosophical/etc. meanings.
The Golden Dawn seized on this ability to take on layers of meaning and made the tarot, as re-designed by Mathers, a centerpiece of their system. Most of this added meaning was not explicit in their deck, however; the cards being more of a mnemonic for teachings that were revealed through other means. They and earlier occultists made all sorts of bogus claims of ancient lineage for the tarot and other teachings, to inspire awe in their initiates. on the spiritual level you could make the claim that they were following paths to enlightenment that have been known since time immemorial, but on a mundane, historical level these claims are 99% hooey: they just made that stuff up. Not to say it isn't true, but it's certainly not factual.
Crowley opted to create a more explicit deck, making the basic occult symbolism the primary focus of the illustrations, and planting hints of deeper mysteries besides. His deck and a number that have followed it use the tarot as a textbook of occult philosophy. The Qabalah is a central part of that. Assigning the pips to the sephiroth was a no-brainer. As for the coincidence factor, ten being the count of our fingers, it's a fundamental number in all human cultures. The alignment of the 22 majors with the 22 paths and Hebrew letters does strike me as more of a coincidence, especially since the original scheme was 21 trumps (3x7) plus the Fool.
There are places where it seems to me also that there is something of a forced fit to the added meanings. Despite having a fair knowledge of astrology, I've never found much value in the astrological attributions that the Golden Dawn added to the cards. With the Qabalah though, I find the Thoth deck has been a great aid in learning the Tree of Life and associated concepts. And that's the real point - the additions are not there to help you read the cards, the cards are there to help you learn the additions.
