Why would Gus get involved with Walt?

Question

Spoiler for Breaking Bad and Better Call Saul (up to Season 6 Episode 11)

In Breaking Bad Season 2, Walt has produced a lot of Blue Meth in the desert together with Jesse. They get via Saul and Mike in contact with Gus who buys all of what they had produced (before they are hired in the Superlab in Season 3).

When just looking at Breaking Bad, I had the impression that Gus bought the Meth just because he already had the network to sell it and it was quite an amount.

However, in Better Call Saul we learn over the time that Gus has a steady delivery from the cartel (and a growing portion since the Salamancas are slightly losing their share). Also, we know from Breaking Bad Season 3 that Gale has already started cooking by himself with a fair quality (not reaching to that of Walt and Jesse, but maybe even better that the quality of the cartel).

Also, in Better Call Saul Season 6 Episode 10 we learn from Mike that Gus finds Walt and Jesse extremely unprofessional, as he and Saul agree that they Walt and Jesse will not last long in the game. Putting all that together (including Gus being extremely paranoid), I don't get why Gus wants to be anyhow involved with Walt and Jesse (given that he has already a solid company running by his own).

So, question is: What is the motivation for Gus to buy that much Blue Meth from Walt and Jesse in Breaking Bad Season 2?

Answer 1

Two Reasons

Gus appreciates quality

Gus wants to cut out the cartel because of his history with them--they murdered his partner and love interest. To do so he builds his own lab. You will note that it is a very sophisticated lab and he recruits a PhD candidate in Chemistry to be his cook. As with Gus's restaurants, he realizes that quality of product is supremely important. It is good for business and he wants to provide it as a matter of principle. To this end, he gets a skilled cook and a state of the art facility. When the extremely pure blue meth appears, Gus wants to be the one providing it. His initial goal is to get Gayle up to speed in cooking that kind of meth. When Gayle dies, he is forced to settle for Walt and Jesse as his cooks.

Gus wants to deny it to the competition

If Gus doesn't buy the blue meth, some other dealer who wants to muscle in on Gus's territory will. Worse, one of Gus's own dealers might buy it on his own and sell it at the expense of Gus's product. By buying it and distributing it to his dealer network himself, Gus maintains control of the market and freezes out competitors and potential competitors. Of course killing Walt would be another way to deny it to them, but as established above, Gus wants to get the secret to doing it himself, first.