Why can a Home Depot with a few large stores provide a higher level of product availability with lower inventories than a hardware store chain such as Tru-Value, with many small stores

Because Home Depot and Tru-value uses different strategies.

Explanation:

Home-Depot being the largest store uses different strategy than Tru-value which makes their products available even with low level of inventories.

Omnichannel fulfillment. Technological investment made by Home Depot. In the first strategy, it make sure that when the customer orders it will get the product, now it's up to warehouses or suppliers to provide it directly to the customer or send it to Home Depot. Secondly, they invest highly in the replenishment process to make it as effective as possible. One additional factor which has the capability to influence the product availability is substitution, customers doesn't care about brand when they shop for hardware.