Original margarine was made from animal fat, which made it much less useful to kosher cooks than margarine. But there was another vegetable product whose adoption presaged the adoption of margarine--crisco!

In the 1800s the fats available to kosher cooks in Europe and America were mostly butter and shmaltz. Shmaltz is a rendered animal fat, usually made from chicken fat. It is solid at room temperature but melts easily. It's somewhat annoying to make, especially if you need to make it a ton, and it lends a slight chickeny aroma to desserts that would otherwise use butter. But it was the only meaty option available. I'm not sure how different this would've been than kosher-meat-derived margarine, if such a product existed. Other cooking oils were not so common.

In the early 1900s Crisco began producing a vegetable-based shortening. They recognized the value of this product to Jewish cooks extremely quickly. After being introduced in 1911 (according to their website), Jewish cooks were one of their first target customer bases. They advertised in Yiddish newspapers. It allowed people to make pastries (pie crusts, for example) without needing to make shmaltz, and those pastries could then be eaten both with meat and dairy meals. This fact was touted in ads, along with its other advantages over shmaltz. They brought in Rabbis to certify Crisco, which was fairly novel at the time--the modern system of commercial kosher certification did not yet exist, attesting to their desire to appeal to this market. And not just any rabbi—Rabbi Moshe Zevulun Margolies, a pretty big name, who they quoted in promotional materials as saying that Jews had been waiting 4000 years for such a product. In the 1930s they even commissioned a bilingual, Yiddish-English, Crisco cookbook

The kosher-keeping world accepted the product. It allowed meat dinners, for Shabbat and holidays, to include tasty desserts that would've been impossible before. Until Crisco, after Friday night dinner your only dessert option was compote. It was so important that the OK, one of the major kosher certification organizations in the US, lists it in their kashrut timeline.

I’m finding a lot less on the introduction of margarine into the kosher world. It seems that post-Crisco, the floodgates were opened for different companies to try their hands at vegetable-based fats (especially a fat that’d give the right texture by being solid at room temperature, like butter, margarine, or schmaltz, and to an extent Crisco as well). Once Crisco existed margarine wasn’t breaking new ground in the kosher world, but over time it won out over Crisco. It is a more versatile product, since you can put margarine on bread or substitute it directly for butter in recipes. I am unaware of any marketing efforts pitching margarine towards Jews. Once Jews were relatively early adopters of Crisco perhaps they didn’t need much convincing to adopt margarine. I’m hoping to find something on this, but hopefully a bit of info on Crisco’s advertising to the kosher-keeping public is close enough and of interest.