The early 1900s was an important time for the history of kosher products. Earlier, observant Jews had made sure their foods were in compliance with dietary laws mostly by personal checking. Their meat was kosher because they took a chicken to the local ritual slaughterer and knew how to prepare it in compliance with the rules of kashrut. Their bread was kosher because the baker was an observant Jew who also kept dietary laws, and this fact was known to people in town/neighborhood. Diets weren't as varied as today, and because families generally cooked things from an earlier step in food production than now, kashrut was a good bit less complicated.

But that wasn't true of all products. Wine and cheese are generally products that require special knowledge in their manufacture, and in the case of wine, a particular climate. A typical family could not so easily make these things on their own, or buy them from someone they knew to be another observant Jew. The "kosher seal" was invented for this purpose. The oldest one is medieval, assuring Rabbinic Jews that the cheese sold by a Karaite was in compliance with Rabbinic law. But these seals became more common with wine, specifically because the laws surrounding wine generally require it to be "double-sealed" when handled by gentiles, and a seal with a signature, particularly one in Hebrew characters, is difficult to replicate. So while the concept of a "kosher seal of approval" existed, it wasn't something that existed widely in Jewish food production.

With industrialization and the migration of Jews from traditional enclaves to cosmopolitan centers that had been a way to buy food from people known to be observant Jews. People didn't know each other as readily, and it would be hard to ascertain someone's actual observance. Outright fraud, selling non-kosher meat as kosher, was quite common. Additionally, with processed foods, it could not be so easily determined whether it had ingredients that would cause kashrut problems. What were once simple foods now had an ingredients list a paragraph long, and what those ingredients actually were wouldn't be so clear.

The solution was drastic expansion of the system of Rabbinic approval of foods. Part of this was individual Rabbis approving particular products, such as the famous example of Crisco, which made kosher-parve pies possible for the first time (dessert pies, that is--meat pies, with a more bread-like and less crumbly crust existed before this). Though it's worth noting I suspect most pies and cookies you could make with chicken fat, a traditional staple of European Jewish cooking, which would render them fleishig (meaty) and would preclude their consumption with dairy meals, but presumably you'd have the dessert afterwards anyway, no? Chicken fat is somewhat difficult to produce in large enough quantities for that, maybe. Another famous example from that period is Coca-Cola, which similarly was certified by an individual Rabbi granting it his approval (though IIRC that was specifically for Passover consumption).

Companies would seek this approval if they wanted the religious-Jewish market. At the time it wasn't a huge market, but for products that were kosher anyway, why not? Kashrut-keepers would otherwise have no way of knowing that a product was kosher and could buy it, and the costs were relatively low. This is a pattern that continued much later--for mass-produced products that were already kosher, paying to have occasional inspections (and approval of the incipient ingredients, which is usually even simpler) is worth it to have the product available to a percent or two of the market. For products that would require change, or are cutting cost by being generic, it's not worth it. Oreos is a famous example--they weren't kosher until quite recently because they contained lard. Once that was removed for health reasons, it was only to Nabisco's benefit to get approval.

But when they did it, they got Rabbinic approval in a new way pioneered in the 20th century, the kosher organization seal. Not long after, seals of individual Rabbis were largely replaced by organizational seals that could deal with the sheer number of ingredients and complicated production of modern foods. Besides this knowledge and experience, Jews wouldn't have to rely on a particular Rabbi being actually competent to certify a product was kosher. If a person said "Rabbi Ploni Ploniwitz said this was kosher", how do you know he knows what he's talking about, or that he's not being defrauded, or that he's even a real Rabbi? An organizational seal prevents this.

Nowadays, Crisco has an OU symbol, rather than a particular Rabbi's signature, which means that the institution's Rabbinic emissaries and procedures certify the product as kosher. There are many more major ones, such as OK, Star-K, Kof-K, CRC, KVH, etc. Nowadays even small local certifications use a copyrighted symbol, rather than a particular Rabbi's seal. This has the advantage of easy customer recognition. It also has the advantage of making the product look more reliable, with serious certifications, which is a not-insignificant part of the reason companies get kosher certification. Some products still have a particular Rabbi's seal on them, but it's not very common, and usually is together with the symbol as an additional certification (i.e. "approved by organization X, and also Rabbi X").

So yes, other companies were getting their products kosher certified, but in 1911 this was quite a small movement, not something done widely yet. It became more common, and with the advent of more processed foods, symbols of Rabbinic organizations replaced individual Rabbis' seals. It wasn't really prized by companies, since most (accurately) viewed the kosher-keeping market as a small one, unless they specifically catered to Kosher consumers. But a slightly bigger market is nice, and they certainly were prized by observers of Kashrut, since it made it substantially easier to find kosher products. Crisco (and margarine more generally) made a big difference, even if they weren't quite as exciting as kosher oreos or non-dairy Ben and Jerry's.