the.com/bandwagon

means To jump on the bandwagon is to support a cause, trend, or side simply because it's already popular or succeeding.

from The bandwagon was literally a wagon that carried a band in a circus parade or political rally — the biggest, loudest float. Politicians in 19th-century America would put their band on a literal wagon to draw crowds, and climbing aboard it became a visible show of support. 'Jump on the bandwagon' caught on as political slang by the late 1800s, then spread into everyday language for anyone who hops onto a winning side once the winning is already obvious.