Yes,​‍​‌‍​‍‌​‍​‌‍​‍‌ large files, in fact, can be converted, but not all tools may work with big CSV files properly. Many online tools give a time-out or stop working when files are beyond a certain size. I had a CSV file with almost 5,000 contacts, and most web converters just went off. What actually did the job was an offline CSV to vCard converter because it deals with contacts locally and thus has no upload limits. GainTools performed the bulk conversion quite effortlessly, probably because it internally processes data in groups. Just make sure your CSV is without any traces of empty rows, strange symbols, or extra commas. After being cleaned, any good CSV to VCF converter will be able to convert CSV to VCF for thousands of contacts without ​‍​‌‍​‍‌​‍​‌‍​‍‌problems.
More info: https://www.gaintools.com/address-book-manager/