Morning Brew gets good sponsorships because of their modern content. Modern content is making video, appealing to a target demographic (Gen Z for them), and being active on social media. Many newspapers don't care enough about social media to realize if they make social media oriented content, they would get sponsorships on those platforms.
I used to work at a large regional newspaper, and they could not understand how social content works. They never made short form content, they refused to make a TikTok or post on Instagram reels or YouTube.
Newspapers have always been supplemented in some way by advertising, but the old people in charge seem to think you can throw some banner ads on your website and call it a day. Sponsorships are a lot different than banner ads.
Thus, you get a bunch of old people reading articles on websites, while the younger people are all on social media. Newspapers also don't understand you can use social content as a way to promote your full newspaper subscription.
The place I worked at was a bunch of people who worked there for 30 years doing the exact same thing as they did on day 1. No desire to appeal to younger people, no desire to compete on social media. Probably because of their arrogance in thinking video or social media is below them and not "real" journalism.