This will become a regular occurrence in the future. T20 leagues are sprouting up all over the world. First we had the IPL, which blocked around 2 months of the international calendar every year. Then Australia came up with the BBL and the ECB created the Vitality Blast. Later, the WICB came up with the CPL, and the Bangladeshis came up with the BPL. South Africa and Pakistan followed with the MSL and PSL respectively. Even Hong Kong, Nepal, Afghanistan and Canada have their own T20 leagues now.
I feel like many cricketers retired from international cricket to prolong their career to play in these leagues world wide as they pay a much bigger pay scale and they gets more time to spend with their family, we cannot blame them for their choice in life, i felt if there was no league like these we would have seen players like AB de Villiers playing for their national team much longer.
It is beneficial for everyone. The T20 format brings in the crowd, the sponsors and the revenue (from sponsorship, as well as from the sale of the broadcasting and streaming rights). The matches last for 3 to 3.5 hours, which is more tolerable compared to 8-8.5 hours needed for an ODI match. Therefore it suit the fans as well.
That said, the retirement of AB de Villiers had nothing to do with the T20 leagues. He had a well publicized altercation with the management during the semi-final of the 2015 CWC and it was the main reason why he ended his career a few years back.
https://www.cricket.com.au/news/south-africa-mike-horn-world-cup-race-quota-vernon-philander-kyle-abbott/2015-04-16Beaten at the semi-final stage by New Zealand in a thriller, controversy erupted after the team that beat Sri Lanka in the quarter-final stage was changed to include fast bowler Vernon Philander ahead of the in-form Kyle Abbott. Philander's selection raised the number of 'players of colour' – a term which encompasses black Africans, mixed-race people and those of Asian descent – to four, the same quota number that was previously implemented until it was abolished in 2007. A report in South Africa's Sunday Times the day after the World Cup final said Philander's selection came at the direction of the Cricket South Africa board
https://www.indiatoday.in/sports/cricket/story/ab-de-villiers-2015-world-cup-semifinal-defeat-autobiography-338539-2016-09-01This is from his autobiography:
So what had happened? Had Vernon, who was officially classified as coloured, been selected ahead of Kyle, who was officially white, to ensure there were four players of colour in the semifinal? Or had the decision been made for purely cricketing reasons?
de Villiers was the captain back then, and this scandal had a very negative impact upon him.