Plants die under water logged conditions …

Waterlogging occurs whenever the soil is so wet that there is insufficient oxygen in the pore space for plant roots to be able to adequately respire. ... There is no universal level of soil oxygen that can identify waterlogged conditions for all plants.
There are at least two reasons why overwatering can harm plants. One reason is a lack of oxygen in a waterlogged soil damages or kills plant roots. Plant roots require oxygen for cellular respiration. You could say plant roots "suffocate" without oxygen. Another reason is that anaerobic microbes in a waterlogged soil produce toxic waste products that can harm plant roots. Thus, even if the plant roots have sufficient oxygen that they obtain internally from aboveground, the roots could still be damaged by the microbial waste products. Microbes in waterlogged soils also promote conversion of some mineral nutrients from nontoxic to toxic forms. For example, in waterlogged soils, nitrate is converted to ammonium, sulfate to sulfide and manganese ion +4 to manganese ion +2.