Something like this?
\documentclass{article}
\usepackage{amsmath,array}
\usepackage[a4paper,left=2cm,right=2cm]{geometry}
\newcommand{\verysloppy}{\tolerance=2000 \hbadness=2000 \emergencystretch=\linewidth}
\begin{document}
\begin{equation*}
\mathrm{Taxonomy}_1=
\begin{Bmatrix}
\mbox{%
\renewcommand{\arraystretch}{1.3}%
\footnotesize
\begin{tabular}{@{} >{$}l<{$} l >{$}r<{{}$} @{} >{\verysloppy}p{8cm}@{}}
D_{1} & Value Proposition & D_1 = & \{C1,7 Blockchain, C1,8 Digital Platform, C1,9 Decision Support System,,C1,10 Marketplace, C1,11 Database, C1,12 Transaction Processing, System\} \\
D_{2} & Value Proposition & D_2 = & \{C1,7 Blockchain, C1,8 Digital Platform, C1,9 Decision Support System,,C1,10 Marketplace, C1,11 Database, C1,12 Transaction Processing, System\} \\
D_{3} & Value Proposition & D_3 = & \{C1,7 Blockchain, C1,8 Digital Platform, C1,9 Decision Support System,,C1,10 Marketplace, C1,11 Database, C1,12 Transaction Processing, System\} \\
D_{4} & Value Proposition & D_4 = & \{C1,7 Blockchain, C1,8 Digital Platform, C1,9 Decision Support System,,C1,10 Marketplace, C1,11 Database, C1,12 Transaction Processing, System\} \\
D_{5} & Value Proposition & D_5 = & \{C1,7 Blockchain, C1,8 Digital Platform, C1,9 Decision Support System,,C1,10 Marketplace, C1,11 Database, C1,12 Transaction Processing, System\} \\
D_{6} & Value Proposition & D_6 = & \{C1,7 Blockchain, C1,8 Digital Platform, C1,9 Decision Support System,,C1,10 Marketplace, C1,11 Database, C1,12 Transaction Processing, System\} \\
\end{tabular}%
}
\end{Bmatrix}
\end{equation*}
\end{document}

tableenvironment here -- that's a "float", and can't be placed inside anything else. Justtabularshould work, although to get the braces around it, it will need to be embedded in math (a display as you have shown) with\text{...}around thetabularblock. – barbara beeton Mar 03 '19 at 23:10texdoc schemata, there are a example of use here – Fran Mar 03 '19 at 23:11