They do it so all current shareholders can sell their shares at a higher price to new shareholders who respond to the pumping advertisements and buy in an irrational frenzy thus driving the share price higher and higher. This will probably happen as suckers will appear and those in the know will play the pump without moral concern to make a quick buck before exiting the stock . The company may also be raising capital by selling an inventory of shares that the market would not buy without the pump. Look out when the game turns south, however, as the fall in share price is very fast after no new suckers are found and all the players have cashed in their shares. With no new buyers, the pumping stops just as rapidly as it started and the dumping is intense. Not everyone can get out in time and the last "in" will lose the most with the share price dropping to near zero. Look at IDNG and PUNL for recent examples of this kind of paid for "pump and dump" scheme.
These mining companies seem to buy up the rights to minerals on properties only to actually resell those rights for a profit and not actually buy equipment to mine anything. MMTE has been buying up thousands of acres of land rights for years, but they are located in NY and haven't mined one bucket of lithium yet.