I'd say it is likely you are running into several different factors working together.
First, this is not generally the best time of year to find a job in most professions. It is a holiday season and HR people and hiring managers have leave to use, so the process is often slower than normal. Next, since it is the end of the year, they may be out of new hire budget until next year.
Additionally, if what you are looking for is an entry level job in your field, the majority of the jobs will be closer to the May/June time-frame when people graduate. At least that is true in the US, not sure when Europeans graduate. While the top tier companies can afford to look early for entry level people, the others have generally found that if they look too early, they may have to hire twice since the students go on looking. So you may have better luck in March.
More than likely at least some of those 50 companies were not interested no matter the timing. Unfortunately many companies don't get bother to get back to people weeded out especially if it was before the interview. It could be that your resume could be improved. You want to make sure you are hitting the key words especially in the ad as many companies do the first cut based purely on keywords and it is automated. It may be possible no one even read the resume.
Next, it appears that hiring freezes are happening in your targeted industry. That means that fewer entry level people will get hired. It means you have to stand out more to get a job in that case and you will have to make many more applications.
And of course, local candidates may get preference over people who have to relocate especially if the company has to pay the costs to get a visa or if it not clear that the visa would be approved (there could also be limits on numbers of visas that will be approved that have run out near the end of the year. This is especially true if the qualifications are roughly the same and even more so when hiring budgets are tight.
So what can you do? First, don't give up, it may take longer than you expected but you will get a job eventually. Accept now that it may take several hundred applications (and if it takes less, think of how happy that will make you.).
Next, really go through your resume and application materials to see if they can be improved. In particular, consider finding a job to be your job right now and thus take the time to individually adjust your resume to target the keywords in the job opening advertisement for each individual job. Consider setting your sights lower as well depending on what kind of jobs you are looking at. If the jobs are not entry level, you may need to look at entry level instead. If you are applying in a language that is not your own, try to find a fluent speaker of that language to help you go over your materials. (and while you are working on getting a job, getting more fluent in the languages used in the countries you want to live in is always a plus.)
Next start building a professional network and look for the unadvertised jobs. If there is volunteer work for conferences for instance, you could meet and potentially impress a lot of the hiring managers.
Find a way to stand out from the crowd. People often forget that they are competing with others for job openings. Be the person whose resume they liked the most. This could mean having personal projects or a very professional blog or a giving a speech at a conference or helping to build something for a non-profit or working on an open source project (if you are a develop). While you are looking, finding things you can do to add to your resume to help you standout will eventually help.
Consider looking locally as well as out of town/country. Sometimes it is easier to get hired when you aren't local if you have some experience and accomplishments to make you stand out. Even if your goal is to move, try locally just to get started. You can always relocate in a year or so instead. The first goal is to get that first job, not necessarily to relocate. I am not saying don't try for those jobs requiring a visa, just don't try only for those jobs.
Finally consider using the resources of your university. Not only the University job center, but also try to hook up with alumni who are in your field. Your professors are also a networking source, They know many of the former students and may themselves have company contacts among hiring managers.
