Oh, actually got a history of why only now, and it's in part because EU and Amnesty International - and it's been over quarter of century of attempting to delegalize the Communists:

In January 2019, the news that the Communist Party was holding its 54th Party Congress, and advancing Petro Symonenko as its presidential candidate, shocked many. Surely the KPU had been banned back in 2015? As it turned out, Ukraine’s Communists are still operating legally.

The KPU was first banned at the peak of perestroika, on 30 August 1991, as a consequence of the failed coup by a section of the Soviet ruling elite. It seemed that the end of Soviet power would bring an end to Ukraine’s Communists, too. Their ideology didn’t really fit in with building a new democratic state with a liberalised economy.

But only two years later, in 1993, the Presidium of the Supreme Council of Ukraine reneged on its 1991 decision, ruling that Ukrainian citizens who support communist ideas can create their own parties. And a few months later, a new “renewed” Communist Party was established via a congress held in Donetsk. Old cadres attempted to get the KPU completely rehabilitated – the party had previously been a member of the Communist Party of the Soviet Union (KPSS), but was, at least formally, considered an independent party. And in December 2001, ten years after the first ban, Ukraine’s Constitutional Court ruled that the renewed Communist party of Ukraine bore no relation to the KPSS, opening the gate for full rehabilitation.

In 2002, a congress was held to unify the “old” and “new” KPU, and Petro Symonenko was elected leader. Later, several other new communist parties were set up, but these groups never attracted a mass membership, although the KPU continued to lose supporters from one election to the next.

This stagnation could have run on eternally if it wasn’t for the events of 2014, when the post-Maidan authorities decided to ban the Communist Party once and for all.

(...)

A>When the Ministry of Justice realised that they couldn’t ban KPU on the basis of criminal accusations, they initiated a new court case based on articles of the “decommunisation law”, as its known in Ukraine.

(...)

In December 2015, the Kyiv city administrative court satisfied the Ministry of Justice’s administrative suit and banned the KPU from operating. This news spread quickly through the media. But these reports did not clarify which case was being discussed, and it was unclear whether this ban related to charges of separatism and treason.

While supporters of the ban cheered, the Communists filed an appeal at the court of first instance. And perhaps, as in the Election Commission’s refusal to register the KPU in the 2015 local elections, the Communists would have lost this case too. But everything changed in May 2017, when 46 Ukrainian MPs called on the Constitutional Court to recognise the “decommunisation law” as unconstitutional.

The Constitutional Court could have already examined this appeal if it wasn’t for a series of circumstances that complicated the “political” side of the decision. A few days after the KPU was banned in December 2015, the Council of Europe’s Venice Commission, which advises and makes recommendations on constitutional matters, made a series of recommendations to the “decommunisation law”. And although the Commission recognised the right of parliamentarians to introduce bans on totalitarian symbols and ideology, the Commission stated that several paragraphs of the decommunisation law were not formulated clearly enough and could be subject to a broader interpretation. This ambiguity concerned a possible ban on certain parties’ operating and participating in elections on the basis of their name, rather than the basis of anti-constitutional activity, as established by a court.

Amnesty International also joined the criticism of the KPU ban, calling on the authorities to withdraw the ban. “The banning of the Communist Party in Ukraine sets a very dangerous precedent. This move is propelling Ukraine backwards not forwards on its path to reform and greater respect for human rights,” said John Dalhuisen, Amnesty International’s Director of Europe and Central Asia. The organisation’s main claim was that the party could be banned or its members prosecuted on the basis of public demonstration of the party’s symbols, rather than any possible genuine offence.

(...)

A paradoxical situation has emerged: the Ukrainian authorities continue to declare pro-EU policy, but in practice the recommendations and warnings of the Venice Commission are ignored. And the Communist Party, which is permitted to operate legally, is once again prevented from participating in elections.

I thought they already did, in like 2015.

A leftoid named Lefteris in the European Parliament didn't like it, years ago: https://www.europarl.europa.eu/doceo/document/E-9-2019-002564_EN.html

These decisions mark a further escalation of anti-communism. They forbid political action by Communists, violating their right freely to disseminate their ideas. They demonstrate the hypocritical nature of the declarations on ‘human rights and freedoms’ and ‘freedom of the press’ that the EU systematically champions whenever it is confronted with governments that are not to its liking and its interests are at stake.

In the case of Ukraine, as well as Poland and the Baltic states, governments with EU support are promoting such provocative anti-communist decisions on the basis of a historically illiterate reading of the past which consists in equating communism with the monstrosity that is fascism. At the same time, the government of the Ukraine and Ukrainian business groups are enjoying the benefits of a series of agreements with the EU, such as the so-called EU-Ukraine Association Agreement, at the expense of the Ukrainian people.

Now murder them all in the fog of war.