Huawei is and wants to build 5G networks across the globe. Given it is essentially a business branch of the Chinese government, there are concerns about the risk this would create to security should there be some issue in the future. Also concerns about privacy of individuals - since we know how China rolls with privacy on things like the Social Credit system.

So Western countries are just a bit anxious to put their communication systems in the hand of a company with these connections. You could also imagine that in the future there could be a whole range of ways that 5G could be used that we don't even necessarily know about yet.

It is definitely a good idea to not trust Huawei - even if they 'might' be ok.