What we call 'Sandcrawlers' are actually the Czerka Corp Multi-Environment Tracked Transport, which makes them ideal for Gorgon siege transports. The METT are Old Republic and Imperial heavy transports that were adapted to carry either personnel or heavy goods like mining equipment and ore, rather than the examples later aquired by Jawas who adapted them to their own purposes.
Millennia before the Battle of Yavin Tatooine seemed a good place to start mining operation. But it appeared that the ore was very poor quality, corroding very fast. The planet's climate and Tusken Raider's attacks were even worse for miners. As a result, companies left the planet beaten by nature, without enough funds to take their heavy equipment with them.
Many sandcrawlers – bulky, yet very sturdy vehicles able to travel even in the most harsh of desert conditions – met this fate. As several different companies made the same mistake of thinking of Tatooine as a great font of resources, this happened several times. The first sandcrawlers were used and left behind on Tatooine by Czerka Corporation, before and during the era of the Sith Wars. Others, brought to the planet on the same purpose by Corellian Mining Corporation, were also abandoned some time later.
The vehicles gained new life thanks to the Jawas, who took to the abandoned vessels as if they were made especially for them. A little-known fact is that Tusken Raiders actually sold some of the vehicles to the Jawas, putting aside their differences for a short time, in the pursuit of monetary profit. This might be the reason why Tuskens from time to time succeeded in raiding a Jawa sand crawler. Equipped with magnetic cranes, energy furnaces, workshops and lots of living and or storage space, sandcrawlers were perfect as mobile headquarters, shops, and homes for the diminutive junk scavengers. Soon, the vessels started to play large roles in Jawa society. One of the most important days for most Jawas was the annual meeting of all sandcrawlers. They were also key in Jawa defense doctrine: the vehicle's armor was strong enough to sustain attack of Sand People or even a Krayt Dragon. However, it proved to be too weak to survive attack provided with effective weaponry. One particular sandcrawler was destroyed by a squad of Imperial Sandtroopers, supported by a Flying Fortress, which easily pinpointed and destroyed weak spots of the desert vessel, immobilizing it and slaughtering all the Jawas.
So now you know
