Tens of billions of dollars in financial assistance from the Chinese government helped fuel Huawei Technologies Co.’s rise to the top of global telecommunications, a scale of support that in key measures dwarfed what its closest tech rivals got from their governments.

A Wall Street Journal review of Huawei’s grants, credit facilities, tax breaks and other forms of financial assistance details for the first time how Huawei had access to as much as $75 billion in state support as it grew from a little-known vendor of phone switches...