Lmao, you clearly don't know what whataboutism is. Both parties have extremists, so examples from both isn't whataboutism, its supporting a statement.
Mamdani should be a shoo-in now for mayor, and its doubtful he'll get to do half of what he says, not least as its not affordable. One Dem in one city, even the biggest in the nation, doesn't define the country. New York is hardly a reflection of likely voters across the nation, and so, a trend does not make. BTW, both the NY Times and the NY Post said not to vote for him, and those papers don't agree on day and night.
As for the embrace of Democrats, he didn't get to 50%, although he will once the transfer voting takes place. That means more Dems voted against him than for him as their #1 candidate. I wouldn't call that being "embraced by Democrats", based on any rational reading of the results. Turnout was at ... 10%.
While he would be expected to win the election, there's no guarantee of that, and his policies are going to be scrutinized and costed to the yazoo ... Adams running as an independent will also mess up the race.