"shows as a ordinary income instead of capital gain"

There's a difference in an Inventory Asset, used to generate a sale, and "business property" as an Asset used in the operation of the business.

A Capital gain, even if you are calling this an investment property, and a Flip, in the IRS terminology, are differentiated by the business purpose.

So, either this activity (the flip) was the business, and this was inventory held over a year end or two while being improved. Or, it is an unusual situation, maybe they bought it to fix and occupy or fix and rent (fixed asset) and then got an offer or otherwise circumstances changed, and they ended up selling it.

Because sales of inventory assets are Ordinary Income.