A lot of people think that speaking in English is easy because it is their mother tongue. But, the truth is that it is not so easy to give a speech in English. The challenges can be many and vary from person to person.
Some people find it hard to pronounce the words properly, and some find it difficult to speak without any pauses. Some people can also not use idioms or phrases that they otherwise use in their native language while speaking in English. Many other challenges like these can make someone's speech sound unnatural or unengaging, which may cause the audience to lose interest.