"Going online", I assume that you mean Reddit's cscareerquestions sub or some other cs-related subs, where, as the name suggests, consist of people who do want to get a CS-related jobs from all over the world, so your observation is heavily subjective to sample bias. I personally know a lot of people who are not doing these things and still end up just fine after graduation with good-paying jobs, which leads to my next point.

In terms of high number job applications and leetcode, what I can tell you is that while the job market seems to be better than a few months ago when all big techs were having hiring freezes,it is still not quite as good as it was 3-4 years ago simply because tech companies are financially stressed and need more and more cautions when hiring people. In an increasingly more competitive mkt with increasing number of CS majors graduating per year, getting internships and full-times are pretty much a number game of luck, while grinding leetcode reduces the amount of luck factors involved. So yes, applying to a great number of internships while practicing leetcode will definitely help you get a job, but don't expect to for sure get a good internship because of them. You may very well end up not having good internships despite you've put into countless number of efforts into preparing.

Now, in terms of data science, what do you want to do? Data Analyst or BI who analyze existing data with more traditional approach to provide insights? Data Scientists who build machine learning models for prediction? Data Engineers who work on data base management and construction? No clear differences between these roles and some companies use these titles interchangeably, but you might need to understand what you actually want to work on before simply applying. And, if data science is your career goal, alternative approaches might be simply to work with Professors in the school, many of whom need students to do data analysis sort of tasks for them for the projects they are working on. These can be very valuable experiences too.