The sensor has a unit_of_measurement and it’s set to hours. The moment a sensor is assigned a unit_of_measurement the UI will present its history graph as a line chart (as opposed to the default bar chart). The unit is “hours” and, so, there you have it.
Unless you have control over unit_of_measurement there’s not much you can do. If you do have control over it, remove it entirely and then you will get a bar chart. If a bar chart is not what you want then you’ve reached an impasse; none of the default history charts suit your needs. In that case, you may wish to explore using a custom graph card such as ApexCharts.